KR101362556B1 - Apparatus and methods for multiple unidirectional virtual connections among sas devices - Google Patents

Abstract

The present invention is directed to an apparatus and method for enabling multiple, unidirectional, virtual connections between a first SAS device and a plurality of other SAS devices in a SAS domain. The improved first SAS device may be configured with two other SAS devices through one or more SAS extenders as appropriate to allow substantially simultaneous unidirectional virtual connection from this first SAS device to both the second and third SAS devices. May be coupled to each substantially simultaneously. Each virtual connection is essentially a half-duplex connection so that the first device can receive information from the third SAS device at substantially the same time as the first device transmits the information to the second SAS device. Improvements are provided by making it compatible with current SAS specifications for connections between devices (eg legacy devices) that have not been adequately improved in accordance with the features and aspects of the present invention.

Description

Method and system for providing a plurality of unidirectional virtual connections between SAS devices, SAS extenders and SAS termination devices TECHNICAL FIELD

This patent application is related to and claims priority in US Provisional Patent Application No. 60 / 882,847, filed December 29, 2006 entitled "Apparatus and Method for Multiple Unidirectional Virtual Connections Among SAS Device."

FIELD OF THE INVENTION The present invention relates generally to SAS domains, and in particular, to apparatus, systems, and methods for multiple unidirectional virtual connections between SAS devices in a SAS domain.

Serial Attached SCSI ("SAS") is a popular protocol and medium that connects the components of a networked storage / computing architecture. In general, the SAS standard defines a SAS domain as including one or more SAS target devices and one or more SAS initiators connected to zero or more SAS expander devices. In general, a SAS initiator device is coupled to a SAS target device as a point-to-point connection. To improve the flexibility of connecting SAS initiator devices to other SAS target devices, a SAS domain is essentially a switched fabric that combines any SAS initiator into a point-to-point connection to any SAS target device in the SAS domain. It may include one or more SAS extenders to provide.

More generally, each of the SAS initiator and SAS target device may be referred to as a SAS end device (or endpoint device) in that multiple devices can sometimes act as initiators and sometimes as targets. Regardless of its role as a SAS initiator or SAS target, any SAS compatible device can attempt to establish a connection with another device. For example, it is common for a host bus adapter SAS initiator device to establish a connection with a SAS storage target device. However, the storage device may later establish a connection with the requesting host adapter again to return the requested read data. Thus, the terms "initiator" and "target" are generally avoided in this discussion. Both the connected initiator and the target device may be referred to herein as "end device" or "endpoint device" or, more simply, "device." An end device attempting to establish a connection with another end device may also be referred to herein as an "opener" or "opening device, while a device that accepts an open request may be referred to as an" off device. "

The SAS standard provides a bidirectional connection between two connected SAS devices. In general, through this bidirectional connection, the opening device can open the device to send the information back to the opener substantially at the same time as when the opening device transmits a frame of information (eg, a “data frame”) to the off device. According to these SAS specifications, this bidirectional connection allows for nearly point-to-point connection between two end devices (some available bandwidth is always consumed by the overhead exchange associated with the protocol). These and other related SAS specifications are well known to those skilled in the art and are readily available, for example, at www.t10.ogr.

In practice, it is sparse that all connected SAS devices (eg, a single disk drive device coupled to an I / O request controller) have data to be transferred to another device in an open connection. RAID storage subsystems (depending on the architecture of the RAID storage controller) Even when the SAS host adapter device is coupled to the SAS device, the host and storage system may rarely fully utilize the available bandwidth of a full bidirectional connection. Thus, the use of a full (or nearly full) SAS connection via true full duplex communication is practically sparse. Rather, empirical test data is shown which indicates that the use of a SAS connection between two devices tends to be less than 50% of the available communication bandwidth. One aspect of this insufficient use stems from the inherent overhead and delays associated with SAS protocols. However, the factor that contributes most to this inadequate use is that the host system (eg, SAS initiator) indicates a request to be completed by the storage device (a single disk drive or more complex RAID or other array-type storage device). Basic communication performed to transmit one or more frames. Storage devices typically require some substantial processing time to complete a request received from the host system. Thus, a SAS target device (eg, a storage device) rarely has data to be sent to the SAS initiator at the same time that the SAS initiator has opened a connection for the transmission of the request. Thus, an open connection is typically closed when the transfer from the reconnected initiator to the target is complete only when the target device attempts to send the requested data back to the initiator.

From the foregoing description, it is clear that there is a need to improve bandwidth usage between the SAS initiator device and the SAR target device in the SAS domain.

The present invention solves the above and other problems by providing a plurality of, unidirectional, virtual connections, systems, and associated methods that are capable of operating substantially simultaneously between a first SAS device and two other SAS devices. Improve the state of the art. Each unidirectional impersonation connection is essentially a half duplex connection, whereby the first device can transmit to the second SAS device while receiving from the third SAS device. This improved mode of operation is still compatible with existing SAS protocols, while providing improved operation with a properly enabled first SAS device coupled to each of a number of other SAS devices through a properly enabled SAS extender. Allow.

One aspect of the invention provides a system comprising three SAS devices, each including a first SAS device, a second SAS device, and a third SAS device coupled to a SAS expander component, wherein the SAS extender component includes: The first SAS is coupled to each of the second SAS device and the third SAS device. The first SAS device and the SAS extender are configured to simultaneously permit a first open connection between the first and second SAS devices and a second open connection between the first and third SAS devices. The first and second open connections use a single link to join the SAS extender to the first SAS device.

Another aspect of the invention provides a method operable in a SAS domain with a SAS extender that couples a first SAS device to each of a second and third SAS device. The method includes establishing a first virtual connection through a SAS extender between the first SAS device and the second SAS device. The first virtual connection is established by the first SAS device and used to send a frame from the first SAS device to the second SAS device. The method also includes establishing a second virtual connection through the SAS extender between the first SAS device and the third SAS device. The second virtual connection is established by the third SAS device and used to send a frame from the third SAS device to the first SAS device. The first virtual connection and the second virtual connection may perform an overlapping operation. The first and second virtual connections use the same link to couple the first SAS device to the SAS extender.

Another aspect of the invention provides a SAS extender configured to couple to at least a first, second, and third SAS device. The SAS extender includes first virtual connection logic configured to establish and operate a first virtual connection between the first SAS device and the second SAS device to transmit a frame from the first SAS device to the second SAS device. The extender also includes second virtual connection logic configured to establish and operate a second virtual connection between the first SAS device and the third SAS device to transmit a frame from the third SAS device to the first SAS device. The first virtual connection logic and the second virtual connection logic are configured to allow the first virtual connection and the second virtual connection, respectively, to perform an overlapping operation.

Another aspect of the invention provides a first virtual connection logic configured to establish and manipulate a first virtual connection through a SAS extender between a SAS terminator and a first SAS device to transmit a frame from the SAS terminator to the first SAS device. It provides a SAS termination device comprising a. The SAS terminator also includes second virtual connection logic configured to establish and manipulate a second virtual connection through the SAS extender between the SAS terminator and the second SAS device to transfer frames from the second SAS device to the SAS terminator. Include. The first virtual connection logic and the second virtual connection logic are configured to allow the first virtual connection and the second virtual connection, respectively, to perform an overlapping operation. The terminating device is configured to establish first and second virtual connections on the same link that couple the SAS terminating device to the SAS extender.

1 is a block diagram of an exemplary system in accordance with aspects and aspects of the present invention for improving bandwidth utilization in a SAS domain;

2 is a block diagram of an exemplary first SAS device and SAS extender improved in accordance with features and aspects of the present invention that allow multiple unidirectional virtual connections between each of the first SAS device and two other SAS devices;

3 is a flow diagram illustrating an exemplary method in accordance with the features and aspects of the present invention operable in an improved SAS domain system in accordance with the features and aspects of the present invention;

4 is a flow diagram illustrating an exemplary method in accordance with aspects and aspects of the present invention for establishing multiple one-way virtual connections between three SAS devices;

5 illustrates an exemplary exchange of SAS transactions between multiple SAS devices and a SAS extender in accordance with aspects and aspects of the present invention.

6 is a block diagram of an exemplary embodiment of an improved expander in accordance with features and aspects of the present invention.

1 is a block diagram of an exemplary system 100 in accordance with aspects and aspects of the present invention for improving bandwidth utilization within a SAS domain. As shown in FIG. 1, a SAS domain (eg, system 100) includes three SAS devices: a first SAS device 101, a second SAS device 102, and a third SAS device 103. ). As is well known in the SAS domain, the first SAS device 101 can connect to a number of other devices (eg, the second SAS device 102 and the third SAS device 103). It is common to include one or more SAS extenders 104 to provide switchable flexibility in providing such a connection. Those skilled in the art will appreciate that any number of SAS devices may be interconnected through any number of associated SAS extenders, subject to limitations of the SAS specification and protocol. Typical SAS domains include substantially more devices and expanders than those shown in FIG. 1. Accordingly, FIG. 1 is simplified only for the sake of brevity of the present description.

In accordance with features and aspects of the present invention, represented by system 100, first SAS device 101 and SAS extender 104 include a plurality of virtual devices between first SAS device and second and third SAS devices 102, 103, respectively. It can be enhanced to allow connections. In particular, a first virtual connection may be established between the first SAS device 101 and the second SAS device 102 in accordance with aspects and aspects of the present invention. Before, after, or substantially simultaneously, the establishment of such a first virtual connection, a second virtual connection may be established and utilized between the first SAS device 101 and the third SAS device 103. As noted above, conventional SAS architectures and methodologies allow for bidirectional point-to-point connections between any two SAS devices. However, conventional SAS architectures and techniques do not allow a single device to communicate substantially simultaneously with both other devices in a SAS domain via a single link connected to a SAS extender.

As used herein, concurrency refers to any aspect of establishing and utilizing two virtual connections. In other words, the establishment of the first virtual connection and the second virtual connection can be virtually overlapped to be performed substantially simultaneously. Or, for example, the utilization of the first virtual connection established above and the establishment of the second virtual connection may be virtually overlapped to be performed substantially simultaneously. Or, for example, all of the previously established virtual connections can be used simultaneously by substantially overlapping data transmissions over the two virtual connections.

As also described above, conventional SAS architectures and techniques allow bidirectional connections between a first SAS device and a second SAS device, but as a practical matter, bidirectional simultaneous communication in such a SAS connection is particularly a host system and a single disk drive. Lack of use in the connection situation between devices. That is, only in a relatively rare situation of a disk storage application of the SAS architecture, both the first SAS device and the second SAS device with which a SAS connection is established can transmit any amount of information in both directions on a single point-to-point full duplex connection.

Thus, in accordance with features and aspects of the present invention, a first virtual connection between the first SAS device 101 and the second SAS device 102 is established for transmitting data frames from the first SAS device to the second SAS device. . The second virtual connection between the first SAS device 101 and the third SAS device 103 is from the third SAS device 103 to the first SAS device 101, ie in the opposite direction to the frame communication of the first virtual connection. Is established to transmit data frames. Thus, in accordance with features and aspects of the present invention, both the first and second virtual connections are substantially unidirectional half-duplex connections. However, as mentioned above, the first SAS device 101 is coupled to two other SAS devices, each coupling configured to unidirectionally exchange information in the opposite direction to the other virtual connections, thereby providing a SAS domain (eg, The processing and communication bandwidth of the system 100 may be better utilized.

The communication path 151 represents a single logical link connecting the first SAS device 101 to a particular port of the SAS extender 104. In a similar manner, SAS extender 104 is coupled to second SAS device 102 via a single logic link 152 and to third SAS device 103 via another logic link 153. The logic connection 151 between the first SAS device 101 and the SAS extender 104 is better used as compared to the conventional SAS standard full-duplex link layer protocol, because each transmission direction of the link 151 is This is because it is coupled to different SAS devices. Rather, two virtual logic connections are established between the first SAS device 101 and the SAS expander 1040.

Although "port", "link", and PHY are well defined by the SAS specification, as used herein, they may be considered as synonyms for description. In general, a link or PHY is a single physical link medium that combines two devices, while a port is a logical construct in SAS. For example, a single port can be a versatile port that oversees the processing of multiple physical links or PHYs. Thus, a port using multiple links may operate some of the multiple links in an improved mode and other links in a standard non-improved mode in accordance with features and aspects of the present invention. However, for a broader scope of the patent, the terms may be considered synonymous in nature.

In one exemplary embodiment of the features and aspects of the present invention, the first SAS device 101 may be an improved SAS termination device, such as a host system or server compute node, equipped with a suitably improved SAS host adapter. . Further, SAS extender 104 allows a single logic connection with SAS device 101, which is enhanced to use a single logic link to establish two unidirectional virtual connections to second and third SAS devices 102,103, respectively. It may be an improved SAS stretcher in accordance with the features and aspects of the present invention. The second and third SAS devices 102 and 103 may be standard SAS devices such as, for example, storage devices or other peripheral I / O devices. The first virtual connection couples the enhanced SAS device (first SAS device 101) to the second SAS device 102 via a logic link 151, an expander 104, and a logic link 152. This first virtual connection is used by the enhanced SAS device 101 to send data frames to the storage device represented by the second SAS device 102. A second virtual connection is established between the first SAS device 101 and the third SAS device 103, for example a second storage device that is desirable for transferring information back to the enhanced SAS device 101. This second virtual connection combines the advanced SAS device 101 and the second SAS device 103 via links 151, SAS extenders 104 and links 153. The data frames generated at the third SAS device 103 are sent back to the enhanced SAS device 101, for example read data is sent back from the storage device to the requesting host system SAS device. Thus, a single logical link 151 that couples the improved SAS device to the improved SAS extender allows for substantially simultaneous transmission from the first device 101 to the second SAS device 102 (eg, writing to storage). Operation) and also more fully by transfer from the third SAS device 103 to the enhanced SAS device (eg, return of read data in response to another host request).

Those skilled in the art will readily appreciate that there may be many additional features and elements in a fully functional SAS device or SAS extender. Such well-known elements are omitted in FIG. 1 for simplicity of the present description.

2 is a block diagram of an exemplary SAS extender 104 improved in accordance with features and aspects of the present invention to allow multiple unidirectional virtual connections between the first SAS device 101 and two other SAS devices 102, 103. .

In accordance with the features and aspects of the present invention, the improved SAS extender 104 includes a separate outbound virtual connect logic element 201 and a separate inbound virtual connect logic element for improved mode communication with the improved first device 101. 202. The outbound virtual connect logic element 201 is an outbound data frame to the second SAS device 102 coupled to the SAS extender 104 (directly or through one or more other insert SAS expanders 252 in the SAS domain). Manage the transport and link layer processing associated with transmitting the data. Inbound virtual connect logic element 202 receives inbound data frames from third SAS device 103 coupled to SAS extender 104 (directly or through one or more other insert SAS SAS 253s within a SAS domain). Manage transport and link layer processing associated with doing The lower level logic PHY control logic 214 is enhanced SAS to a corresponding single link of the enhanced SAS extender 104 that allows the first SAS device 101 to communicate with the second and third SAS device modes. Physically couple the expander 104.

The outbound virtual connection logic 201 is a standard SAS protocol transport and link layer state machine that transmits data frames from the first SAS device 101 to the second SAS device 102 in accordance with the SAS credit protocol and handshake. Outbound transmission and credit logic elements 206 that serve to manage the < RTI ID = 0.0 > In a similar manner, the inbound virtual connect logic element 202 receives link and transport layer management according to a standard SAS state machine model when it receives an inbound data frame from a third SAS device 103 attached to the first SAS device 101. It may include inbound receiving and credit logic 212 generally responsible for the.

The duplexing logic element 203 prevents inbound data frame transmission from the second SAS device 102 to the first SAS device 101 (eg, typically receives from a third SAS device). Performing specialized state machine processing associated with features and aspects of the present invention to avoid transmission of outbound data frames from the third SAS device 103 to the first SAS device 101 by ignoring or discarding the credit indication). Represents a combination and / or sequential logic. In particular, the doubled logic element 203 can include inbound credit blocking logic 208 that generates a CREDIT BLOCKED primitive for transmission to the second SAS device 102. Preferably, when establishing a first virtual connection with the second SAS device 102, the inbound credit blocking logic element 208 immediately sends a CREDIT BLOCKED prototype so that the improved first SAS device 101 can transmit the second SAS device 102. Inform the second SAS 102 that it will not receive any data frame transmission from the device. Similarly, the doubled logic element 203 can generally include outbound credit discard logic 210 operable to avoid outbound transmission from the improved first SAS device 101 to the third SAS device 103. This avoidance of outbound transmission is simply processing that ignores any RRDY prototype received from the third SAS device 103 used for example to indicate receive buffer space for receiving the transmission from the first SAS device 101. Can be represented. The other logic in the improved first SAS device 101 never attempts to transmit a data frame to the third SAS device 103 based on the improved mode of operation to simply establish multiple unidirectional virtual connections.

As implemented within SAS extender 104, outbound virtual connection logic 201 and inbound virtual connection logic 202 are associated with three PHY control logic elements. PHY control logic element 214 implements PHY control that couples SAS extender 104 into an improved first SAS device 101 over a single link. PHY control logic element 221 couples outbound virtual connection logic 201 to a second SAS device (eg, a storage device or other peripheral device) via a single link. The PHY control logic element 222 transfers the inbound virtual connection logic 202 to the third SAS device 103 (e.g., another storage device that requires a connection to the first SAS device to send a data frame). To combine.

Thus, the improved SAS extender 104 is configured to establish a first virtual connection that couples the improved first SAS device 101 to the second SAS device 102. This first virtual connection stores a data frame from the first SAS device 101 to the second SAS device 102, for example, storing the SAS from the host system SAS adapter device, as in the processing of a write request from the SAS host device. And transmit the data frame sent to the device. In operation of the first virtual connection, the improved SAS extender 104 receives a data frame via the control logic 214. Data frames received from the enhanced SAS device are transmitted over the PHY control logic 221 via outbound virtual control logic 201 and in conjunction with standard routing logic in the enhanced SAS extender 104 to transfer this logic link. Is sent to the second SAS device 102.

The improved SAS extender 104 is also configured to establish a second virtual connection that couples the first SAS device 101 to the third SAS device 103. This second virtual connection may be used to retrieve a data frame from a third SAS device for processing within the first SAS device, for example, a data frame sent from the SAS storage device back to the host system SAS device as in the processing of a read request. Is configured to receive. In operation of this second virtual connection, the improved SAS extender 104 receives a data frame from the third SAS device 103 via the PHY control logic 222. These received data frames are sent to the PHY control logic element 214 via the inbound virtual connection logic element 202 and to the improved first SAS device 101.

Thus, the improved SAS extender 104 provides two unidirectional virtual connections, a first virtual connection between the first SAS device 101 and the second SAS device 102, and a first SAS device 101 and a first virtual connection. And configured to establish a second virtual connection between the three SAS devices 103. The first virtual connection is used to transfer the data frame from the first SAS device to the second SAS device, while the second virtual connection is used to transfer the data frame from the third SAS device to the first SAS device.

Those skilled in the art will readily appreciate that a variety of different and additional elements may be used within the improved SAS stretcher 104 that is fully operational. These additional elements have been omitted in FIG. 2 for the sake of simplicity and clarity of the present description.

In an exemplary preferred embodiment, the improved features and aspects of the present invention may be distributed to combination and / or sequential logic added to both the improved SAS expander and the improved SAS device. The advanced SAS device may be properly configured to request that its connection to the SAS extender should be enabled for the improved mode of operation. An improved SAS extender in accordance with features and aspects of the present invention responds to the request of the improved SAS device by permitting improved mode operation. Legacy SAS extenders that do not have the improved features and aspects of the present invention can reject new requests from improved SAS devices and simply continue to operate in the standard SAS mode of operation. Thus, an improved SAS device must be compatible with past SAS extenders to continue to operate according to the SAS extender when not connected to a suitable improved SAS extender.

3 is a flow diagram schematically illustrating an exemplary method in accordance with the features and aspects of the present invention operable in an improved SAS domain system in accordance with the features and aspects of the present invention. As described above, features and aspects of the present invention allow a SAS domain to establish a dual, unidirectional virtual connection between the first SAS device and the second and third SAS devices. Thus, element 300 of FIG. 3 is first operable to establish a first virtual connection between a first SAS device and a second SAS device. For example, the first SAS device may be a host system or server with a suitable host bus adapter, and the second SAS device may be a storage device such as a disk drive or other similar storage device. This first virtual connection is used to transfer a SAS data frame from the first SAS device to the second SAS device. Such data transfer may be, for example, in response to processing of a host system or server write request to send information to a storage device. This first virtual connection is preferably established in a manner that prevents data frames from being transmitted in the reverse direction, ie from the second SAS device to the first SAS device. Thus, additional bandwidth will be available to other storage devices that are currently preparing and waiting to send data frames to the first SAS device. Element 302 is operable to establish a second virtual connection between the first SAS device and the third SAS device. This second virtual connection is generally used to transfer data frames from the third SAS device back to the first SAS device. Such a transfer may, for example, cause a third device (e.g., a storage device) to ultimately return the requested data to the first SAS device (e.g., a host system or server node with an appropriate SAS host bus adapter). If so, it may be in response to processing of a host read request. Since this second virtual connection with the first SAS device is used to return data to the first SAS device, the transmission of data frames from the first device to the third device over this second virtual connection is preferably excluded. . When using both established one-way virtual connections, element 304 may operate both virtual connections such that transmissions substantially overlap in both the first and second virtual connections. In other words, the first virtual connection can be used more fully to transfer information from the first SAS device to the second SAS device, while the second virtual connection allows any third SAS device to send information back to the first SAS device. And remain available for transmission.

Those skilled in the art, all of the various steps in the detailed implementation of elements 300-304 may overlap as well as the data being transmitted after the establishment of both virtual connections. In other words, there is a need for a first virtual connection to be established and a second virtual connection to be established (e.g., when a third SAS device attempts to send information back to the first SAS device and can also transmit). Start transmission before it occurs. Thus, establishment of the second SAS virtual connection may overlap the data frame transmission of the already established first virtual connection and / or overlap the lower level of operation for establishing the first virtual connection. In a similar manner, the first virtual connection may not be established yet or may be completed and closed, while the second virtual connection remains operational. Thus, the first virtual connection can be established while substantially overlapping the ongoing operation of the previously established second virtual connection. In other words, no particular order or sequence is necessary to establish the first connection and the second connection. These connections may be established and used in essence in any useful sequence, depending on the specific needs of data transmission in the applicable SAS domain.

Those skilled in the art will recognize many equivalent and additional method steps that may be included in a fully functional method in accordance with the features and aspects of the present invention. These additional details are omitted in FIG. 3 for simplicity and clarity of the present description. Furthermore, those skilled in the art will recognize that the method of FIG. 3 represents a wide range of aspects of operating the system in accordance with the features and aspects of the present invention. Certain detailed processing for aspects of FIG. 3 may be used exclusively in the improved SAS device, exclusively in the improved SAS device, or distributed through both the improved device and the improved device of the SAS domain. .

Furthermore, those skilled in the art will appreciate that certain conditions of the requested predetermined protocol exchange by one or more devices combined in a SAS device, SAS extender, SAS domain as a whole, or in an enhanced mode of operation may be adjusted to be completed between the devices. It may require termination of the improved connection before the request or indication. For example, if a device currently included in such an improved connection requires an opening of an STP SAS protocol exchange, this improved connection may interfere with its operation. Thus, the improved connection may be closed or terminated if such conditions are detected in any device or expander included in the improved connection.

Thus, FIG. 3 attempts to represent an exemplary wide variety of methods in accordance with aspects and aspects of the present invention regardless of whether such processing is performed. As mentioned above, in the exemplary embodiment the processing of the method of FIG. 3 is preferably distributed between the enhanced SAS devices requesting the ports of the improved SAS extender for improved mode operation on their links. The improved SAS extender and the improved SAS device can work together to better utilize the available bandwidth of the established connection by performing the method of FIG. 3.

4 is a flow diagram illustrating an exemplary method in accordance with aspects and aspects of the present invention for establishing multiple one-way virtual connections between three SAS devices. Element 400 is first operable to establish an improved mode of operation between the first SAS device and the SAS extender. As mentioned above, in an exemplary embodiment of the features and aspects of the present invention, the steps involved in the processing of the method of FIG. 4 are performed between the improved first SAS device and the improved SAS extender to which the first device is coupled. Can be distributed cooperatively. The improved features and aspects of the invention are preferably implemented while maintaining compatibility with existing standard SAS devices (eg, "legacy" devices). Thus, the improved features and aspects of the present invention are advantageously provided by the enhanced SAS device requesting that the improved SAS extender, to which the improved SAS device is coupled, enters an improved mode of operation in connection with this improved SAS device. May be enabled.

New transaction messages and responses may be exchanged between the first device and the extender to enable the enhanced mode. If the expander responds positively, the following improved mode processing can be initiated. If the expander fails to handle the enhanced mode processing (e.g., a legacy expander), the expander will reject the new command or message and a standard compatible SAS protocol rather than the improved method of FIGS. Will be used. Alternatively, the enhanced mode can be requested by special vendor specific parameters for existing SAS transactions. In a similar manner, if the expander can handle this improved mode, the expander will initiate the improved mode operation in a positive manner in response to the request. The detailed structure and fields of these new messages or transactions between the SAS device and the SAS extender will certainly be a matter of design choice for those skilled in the art.

In this enabled enhanced mode, the processing of elements 402-404 can be repeated while substantially overlapping with the iterative processing of elements 420-434. In general, elements 402-410 may be operable to establish and use a first virtual connection between an improved first SAS device and a second SAS device. The first SAS device is preferably coupled to a port of the enabled SAS extender for improved operation that is enabled by the operation of element 400. The second SAS device may be coupled to any other port of the SAS extender or may be coupled anywhere within the SAS domain reachable through the SAS extender to which the first device is coupled.

Element 402 describes the requirements for establishing a first virtual connection. This requirement arises when an improved first SAS device in accordance with features and aspects of the present invention needs to transmit information to a second SAS device. In particular, although the first SAS device needs to send a data frame to the second SAS device, the second device may not send information back to the first SAS device. If this need arises, element 404 establishes a first virtual connection between the first SAS device and the second SAS device so that data frames can be transmitted from the first device to the second device. As mentioned above, an example of such a transmission may be in response to the processing of an I / O write request on a host system or server node comprising a SAS host bus adapter device, or, for example, in response to an I / O read request. In response to returning the requested data from the SAS storage device to the requesting host system. The establishment of such a connection uses well known SAS prototypes, including, for example, open frame address prototypes and associated open accept and / or open reject prototypes in response thereto. However, as mentioned above, this unidirectional first virtual connection is limited to data transmission from the first device to the second device. Thus, element 406 next immediately sends a CREDIT BLOCKED prototype to the second SAS device to indicate that the first SAS device will not accept any data frame transfer returned from the second SAS device. The use of such CREDIT BLOCKED prototypes and their associated protocols is well known to those skilled in the art as described in the SAS specification. Next, element 408 is operable to transmit a data frame on the first virtual connection from the first SAS device to the second SAS device using the established first virtual connection. This data transmission is performed in accordance with standard SAS usage and protocol using the received credit handshake information provided by the second SAS device. When element 408 has completed the transmission of all data frames to be transmitted to the second device, the first virtual connection will be closed by operation of element 410 according to standard SAS protocol. Processing then returns to element 402 to wait for the requirement to establish another first virtual connection from the same first SAS device.

As mentioned above, elements 420-434 are operable substantially simultaneously with elements 402-410. Elements 420-434 are generally operable to establish and utilize a second one-way virtual connection used to transfer information from a third SAS device to the same first SAS device of the first virtual connection. This operation may be performed in response to, for example, a host read request and the addressed storage device (eg, a third SAS device) is delayed in preparing to return the requested data. This delay is common in rotating disk drive storage, for example. Thus, element 420 is operable to wait for the need to establish this second virtual connection first. This second virtual connection is considered to be required when a given third SAS device requests establishment of a connection with the first SAS device (eg, to return the requested read data). If such a request is detected, element 422 is then operable to establish a second virtual connection between the first device and the third SAS device such that the data frame is transmitted from the third device back to the first SAS device. do. As mentioned above with respect to element 404, this unidirectional second virtual connection allows the data frame to be sent only from the third device to the first device. Thus, the first device will ignore the received credit information received from the third SAS device and / or simply will not attempt to transmit from the first device to the third device (in the opposite direction of this second virtual connection). . Elements 424-432 are repetitively operable to receive all frames to be sent from the third device back to the first device. Specifically, element 424 receives one or more frames sent from the third SAS device back to the first SAS device over the second virtual connection. Element 426 represents standard SAS specification and protocol processing to manage the transmission credits through the received credits and corresponding PRDY prototypes. Element 428 represents the processing described above within the first SAS device that ignores any received credit information associated with the receipt of a frame on the third SAS device. Reception on this third SAS device is independent of this second virtual connection for unidirectional operation from the first SAS device to the third SAS device. Other SAS devices may asynchronously attempt their own connection to the first SAS device (eg, when it is ready to return data to the requesting first SAS device). This additional connection request may be rejected until this second virtual connection is closed. Thus, element 430 represents processing to ignore or reject any subsequent connection request from another SAS device when communication with the first SAS device is currently needed. Element 432 determines whether additional receive frames from the third SAS device are expected. In such case, processing continues back to element 424. Otherwise, element 434 next closes the second virtual connection and returns to element 422 waiting for the need to reestablish a connection with the same or another SAS device and the first SAS device. In particular, a device rejected or ignored by the operation of element 430 may retry to establish this connection and once again resume processing of elements 420-434 to establish a new second virtual connection. do.

Those skilled in the art will recognize various equivalent and additional method steps that may be used in a fully functional system operating in accordance with the method of FIG. In particular, element 400 has been described above as representing processing to establish an improved connection mode between an improved first SAS device and an improved SAS extender in accordance with features and aspects of the present invention. The improved mode of operation may also be interrupted at any time if the improved first device sends an appropriate command to abort the enhanced mode of operation. The specific commands or prototypes associated with establishing and interrupting this improved mode of operation will obviously be a matter of design choice for those skilled in the art.

Furthermore, as described above, those skilled in the art will appreciate that the method of FIG. 4 is performed only in an improved SAS device, only in an improved SAS extender, or more preferably in an improved SAS device and in which the device lacks. It will be appreciated that this can be done cooperatively between SAS stretchers. Furthermore, certain, combinatorial and / or sequential logic and state machine changes to implement the method of FIG. 4 will be readily understood by those skilled in the art familiar with the SAS specification and state machine defined herein.

5 illustrates an exemplary exchange of SAS transactions between multiple SAS devices and one SAS extender in accordance with aspects and aspects of the present invention. In FIG. 5, time proceeds downward in the figure. Each series of directional horizontal arrows represents a SAS message / circular exchange from the first SAS component to the receiving SAS component. The start of the arrow is associated with the vertical line representing the SAS component sending the corresponding message, and the arrow end of the directional arrow ends at the vertical line corresponding to the receiving component of the message being delivered. The message exchange illustrated in FIG. 5 includes a first SAS device (eg, a SAS initiator or target device) represented by a first vertical line from the left side of the figure, and a SAS represented by a second vertical line from the left side. A second, both coupled to the expander and corresponding ports of the same SAS expander, each representing a SAS device (e.g., a target device such as a storage device within a storage subsystem or another initiator / host device); Represents an exchange within a SAS domain with third and fourth SAS devices.

Arrow 501 represents the transfer from the first SAS device DEV1 to the SAS expander EXP, which transmission may cooperate to allow improved operation in accordance with the features and aspects of the present invention. To ask. The particular SAS transaction (ie, the message to be delivered from the first SAS device to the SAS expander) can be any useful message as a matter of design choice. In response to the message corresponding to arrow 501, arrow 502 may indicate a response from the SAS expander to the first SAS device indicating acceptance of the enhanced mode of operation request. If the SAS expander is a legacy device that does not support the enhanced mode of operation, then this enhanced behavior is accompanied by an appropriate rejection message informing the first SAS device that this particular SAS domain is not allowed (through this particular SAS expander). 1 Can be returned to the SAS device.

If an enhanced mode of operation is established between the first SAS device and the SAS extender, arrow 503 indicates a standard open connection request that is passed (via the middle SAS extender) from the first SAS device to the second SAS device DEV2. Indicates. This open connection request is a standard SAS request that uses an open address frame request for a particular connection and sets certain parameters for that connection. In response to accepting the first unidirectional virtual connection, the second SAS device returns a standard RRDY prototype to the first SAS device to indicate the credit available for receipt of the data frame to be sent from the first device. In practice, many such RRDY prototypes represent the number of buffers transmitted from the second SAS device to the first SAS device and available for storing received frames. Credit protocols used to control the flow of messages between first and second SAS devices are well known to those skilled in the art.

According to the features and aspects of the present invention, the connection established between the first SAS device and the second SAS device is in this improved mode only a frame from the first SAS device to the second SAS device, i.e. the first unidirectional virtual connection. Used to transmit via In order to prevent the second SAS device from attempting to return information to the first SAS device via a data frame transfer, the first SAS device is preferably CREDIT to the second SAS device as shown by arrow 505. You can send a BLOCKED prototype. The CREDIT BLOCKED circle is a standard SAS circle used to indicate that the first device receives or is not expected to receive a data frame from a second SAS device.

The third SAS device DEV3 may be configured asynchronously to return information to the first SAS device and thus request an open connection to it. Arrow 506 represents a standard SAS open connection request that is passed from the third SAS device to the first SAS device through an intermediate SAS extender. According to the improved mode of operation, the SAS expander allows open requests to be delivered on the first SAS device so that a second one-way virtual connection for data transfer in the opposite direction, i.e. from the third SAS device to the first SAS device. Will allow establishment of Arrow 507 represents the standard open accept circle returned from the first SAS device to the third SAS device via the intermediate SAS extender. Thus, a second unidirectional connection is established between the first SAS device and the third SAS device. The second unidirectional virtual connection is used to transmit the data frame to the first SAS device, while the first virtual connection established above is used to transmit the data frame from the first SAS device to the second SAS device.

By establishing a dual unidirectional virtual connection with the first device, the utilization of SAS ports / links that couple the first SAS device to the SAS extender can be improved over prior art. The prior art allows full duplex communication over a single logic link between two devices, but the need for a single disk drive storage device, or a combined initiator and target in an open connection, to simultaneously transmit data frames in both directions. In a SAS connection to a given RAID storage system, the double communication is rare. According to features and aspects of the present invention, through two unidirectional virtual connections established by the messages represented by arrows 501-507, the first device transmits frames to the second SAS device while at the same time from the third device. Data can be received.

In response to establishing the second unidirectional virtual connection, the first SAS device returns to the third SAS device a standard RRDY prototype that represents the credit available for receipt of the data frame transmitted from the third device. Indeed, many such RRDY prototypes represent the number of buffers available for storing frames received from the first SAS device to the third SAS device. Credit protocols used to control the flow of messages between first and third SAS devices are well known to those skilled in the art. The improved features and aspects of the present invention distinguish credit management logic for each of the two unidirectional virtual connections, but otherwise essentially the same state machine for the credit management protocol as described in the SAS specification, which is well known to those skilled in the art. Use

At any time while the second one-way virtual connection is being established, another device may be ready to send data back to the first SAS device. Arrow 509 represents this open connection request sent back from the fourth SAS device DEV4 to the first SAS device. An improved feature of the SAS extender intercepts open requests and returns an open reject SAS prototype indicating that a second virtual connection is currently established. According to standard SAS protocol processing, the fourth SAS device may repeat the open request until the time the request is accepted or the total number of timeouts or retries is exceeded. Accordingly, arrows 511 and 512 indicate repetition of attempts to establish an open connection between the fourth SAS device and the first SAS device, and a second rejection based on the currently established second virtual connection. Those skilled in the art will readily appreciate that the specific number of retries attempted by the fourth SAS device to establish this new connection and the duration of the timeout value associated with that attempt is a matter of design choice for a particular SAS domain and application. Could be. In another embodiment, rather than rejecting the open connection request, the enhanced SAS expander may return the AIP prototype to the fourth device to actually "stall" the open request until the current virtual connection is terminated. have. This AIP prototype is known within the SAS protocol and indicates that the requested connection is currently in use. Thus, according to the known SAS protocol, the fourth device can be suspended until the current virtual connection is terminated. The "stopped" open request of the fourth device may be sent to the first SAS device to establish another second virtual connection.

Groups of related arrows 514.1 through 514.6, collectively identified by reference number 514, may indicate substantial overlap for the exchange via the first virtual connection and the second virtual connection. As mentioned above, the first virtual connection is used to transfer data frames from the first SAS device to the second SAS device, while the second virtual connection transfers data frames from the third SAS device to the same first SAS device. It is used to Arrow 514.1 indicates one or more data frame transfers from the first SAS device to the second SAS device using the first virtual connection. In response, arrow 514.2 represents one or more RRDY primitives returned from the second SAS device to the first SAS device using the first virtual connection, with the transmitted frame buffered and ultimately consumed in the second SAS device. . Arrow 514.3 represents the transmission of one or more data frames from the third SAS device to the first SAS device using the second virtual connection. Arrow 514.4 indicates the resulting return of the ACK prototype from the second device using the first virtual connection to the first SAS device. Arrows 514.1 and 514.6 indicate the resulting return of the RRDY and ACK prototypes from the first SAS device to the third SAS device using the second virtual connection. Thus, Figure 5 shows the substantial overlap of messages exchanged between three SAS devices (SAS device 1, SAS device 2 and SAS device 3) by using two open virtual connections simultaneously.

The group of messages represented by reference number 514 includes the transmission of data frames in both directions (e.g., 514.1 and 514.3) and the transmission of RRDY and ACK prototypes (e.g., 514.2) in response to receiving the transmitted frames. , 514.4, 514.5, and 514.6). Those skilled in the art will readily appreciate that the various messages exchanged over the two virtual connections may actually overlap if not completely. Messages exchanged over any single connection of the virtual connections may be exchanged in the proper order and sequence according to the SAS protocol. In other words, transmission of the frame over the first virtual connection 514.1 must precede the corresponding RRDY and ACK primitives 514.2 and 514.4 returned from the second SAS device to the first SAS device using the first virtual connection. There is a need. In a similar manner, a data frame 514.3 sent on a second virtual connection from a third SAS device to a first SAS device on a second virtual connection is generated from the first SAS device to the third SAS device using the second virtual connection. Must necessarily precede the corresponding RRDY and ACK prototypes 514.5 and 514.6 returned by. However, the various transactions 514.1, 514.2 and 514.4 on the first virtual connection may substantially overlap with the transactions 514.3, 514.5 and 514.6 on the second virtual connection.

Those skilled in the art will readily recognize various additional or alternative SAS messages and transactions that may be exchanged between the various devices. Such additional messages have been omitted in FIG. 5 for the sake of simplicity of the present description. Thus, FIG. 5 is considered to be an illustration of some simple message exchanges that may overlap between various SAS devices in accordance with aspects and aspects of the present invention. In particular, an open, established virtual connection may be closed by the operation of the device associated with the established connection. For example, if the second virtual connection is closed by the operation of either the first SAS device or the third SAS device, another SAS device (eg, the fourth SAS device) may have data from the fourth device to the first device. A second virtual connection may be reestablished that couples the fourth SAS device to the first SAS device to transmit the frame. Furthermore, further improved messages may be exchanged between the first SAS device and the SAS expander to terminate the improved mode of operation. The improved mode of operation may be terminated for any number of reasons determined by the first SAS device and / or SAS expander, respectively, in accordance with features and aspects of the present invention. If such an improved mode of operation ends, the transaction between all the devices presented in FIG. 5 will operate according to existing standard SAS protocols and specifications.

Furthermore, those skilled in the art will readily appreciate that no specific order is required in establishing the first and second virtual connections. In other words, the first virtual connection may be established by a third SAS device wishing to return the data frame to the first SAS device. Subsequent to establishing this connection, a second virtual connection may be established between the first and second SAS devices to transmit data frames from the first SAS device to the second SAS device.

6 is improved in accordance with features and aspects of the present invention to provide a connection between a first SAS device and two other SAS devices that are improved to allow substantially overlapping communication between each of the first device and the other SAS device. An exemplary embodiment for a SAS expander is shown.

6 illustrates the functional elements for a simplified, exemplary improved SAS expander 104 having two standard PHY layers 602, 604. Each standard PHY layer 602, 604 includes a corresponding attached SAS device and receive logic 621, 623 and transmit logic 622, 624 for receiving and transmitting SAS information, respectively.

The improved SAS extender 104 includes an improved port / link 600 that is coupled to an improved SAS device (ie, a first device (not shown)). The enhanced port / link 600 includes a standard PHY layer 612 with respective receive logic 616 and transmit logic 618 that receive and transmit SAS information for the attached enhanced first SAS device. do. The enhanced port / link 600 is also coupled between the first device coupled to the enhanced port / link 600 and the second SAS device coupled to the standard PHY layer 602 and coupled to the standard PHY layer 604. An interleaver 610 and a demultiplexer 614 to coordinate simultaneous connections between the third SAS device and the first SAS device. The improved SAS extender includes an RX monitor and connection control logic 640 and a clover switch 650 for coordinating concurrent virtual connections.

If the control logic 640 detects that the enhanced mode operation is not used (ie, no enhanced mode command and / or virtual connection request is made), then the signal applied to the control bus 630 is interleaved. 610 and the improved processing by the demultiplexer 614 and also simply disable the crossbar switch 650 for normal operation, that is, for normal operation of a complete double point-to-point connection between the two devices. ). In other words, the improved SAS extender 104 can configure the enhanced port / link 600 to be used as any standard SAS port.

In enhanced mode operation (i.e., detecting a set of instructions or instructions requesting an enhanced mode operation), control logic 640 monitors the set of SAS instructions exchanged on the receive logic of all three ports 616, 621 and 623. A control signal "A" is applied to the control bus 630 to control the interleaver 610, the demultiplexer 614, and the crossbar switch 650. The control logic 640 monitors a set of instructions received from any of the three ports to monitor the first and second virtual connections, for example, between the first and second devices and the first and second virtual connections. The crossbar switch 650 is configured to establish and terminate a second virtual connection between the first device and the third device. Any device can close or terminate the virtual connection with another device.

During operation of the first and second virtual connections (ie in an improved mode with at least one established virtual connection), control logic 640 transfers the set of instructions from one device to the appropriate other device of the corresponding virtual connection. The transmission controls the operation of the demultiplexer 614 and the interleaver 610 of the enhanced port 600 to coordinate the simultaneous use of both virtual connections. This coordination involves the buffering and / or queuing of the instruction set such that the instruction set is not lost in the virtual connection and the important instruction set is delivered to the appropriate device and in the proper order as needed.

For example, a first virtual connection is established between a first device (coupled to an improved port 600) and a second device (coupled to standard PHY logic 602) to connect from the first device to the second device. It is assumed that the data transmission of. Furthermore, assume a second virtual connection between the first device and the third device (coupled to standard PHY logic 604), for example, for data transfer from the third device to the first device.

For this exemplary first virtual connection, the data indication set transmission will generally govern the exchange from the first device (on the improved port 600) to the second device (on the standard PHY 602). This set of data indications is generally passed from the receive logic 616 of the enhanced port 600 to the transmit logic 622 of the standard PHY 602 via the demultiplexer 614 and the switch 650 and the paths 668,662. Will be. In a similar manner, data indication set transmission will generally govern the exchange from a third device (on standard PHY 604) to a first device (on improved port 600). This set of data indications is generally via a switch 650 and an interleaver 610 via paths 666 and 664 from the receive logic 623 of the standard PHY layer 604 to the transmit logic 618 of the enhanced port 600. Will be delivered.

A set of data indications may govern the transmission entering the interleaver 610 for application from the reception logic 623 to the transmission logic 618, but for example protocol handshake, opening and closing of connections, flow control, and the like. An indication set from receive logic 621 may also be received for this purpose. In a similar manner, a set of data indications from receive logic 616 to transmit logic 622 dominate transmission via demultiplexer 614, but are sometimes received for protocol handshakes, open and close connections, flow control, and the like. The set of instructions from logic 616 will be sent to transmit logic 624 via demultiplexer 614. Accordingly, demultiplexer 614 receives a set of instructions from the receive logic 616 of the enhanced port 600 and passes the received set of instructions through the switch 650 via the path 666 to the standard PHY layer 602. Or via path 668 to the standard PHY layer 604. Control logic 640 adjusts the selection of the path and configures switch 650 appropriately. Further, interleaver 610 receives the instruction set from receive logic 621 via path 662 or receives logic 623 via paths 664 and 668 and applies the received instruction set to logic 618. It is configured to. Interleaver 610 coordinates this communication in conjunction with control signal 630 generated by control logic 640 to configure switch 650.

Demultiplexer 614 is generally used as transmit logic 622, for example with receive logic 616, or as transmit logic 624 (when adjusting the configuration of switch 650 with control logic 640). Combination and / or sequential logic that may implement a state machine to coordinate the transmission of the data set of the < RTI ID = 0.0 >

Interleaver 610 generally includes combination and / or sequential logic that can interleave a set of instructions received from receive logic 621 or receive logic 623 for application to transmit logic 618. Interleaving (associated with the monitoring feature of control logic 640) may detect available idle periods among the main transmissions of data frames from receive logic 623. Until such an idle period is detected, the indication frame received from receive logic 621 for application to transmit logic 618 may be buffered / queued for subsequent applications. If the control logic 640 and the interleaver 610 consequently identify an idle period, the buffered / queued set of instructions (if any) may be sent from the queue to the first device via the transmit logic 618.

The functional element of the improved SAS extender 104 shown in FIG. 6 represents an exemplary possible decomposition of one of the functions performed. Those skilled in the art will recognize many similar and equivalent functional breakdown elements having the features and aspects of the present invention in an improved SAS stretcher. In particular, the detailed design and implementation of the logic features described above will be readily appreciated by those skilled in the art as a matter of design choice. Also, those skilled in the art will provide a number of such improved ports 600 and extend the enhanced expander 104 such that all of these ports can be combined with each other to establish multiple virtual connections between them. It will be easy to understand the extensions to the described functional elements. Thus, FIG. 6 is only one example of one possible embodiment of the features and aspects of the present invention.

As mentioned above, the improved interleaver's interleaver temporarily stores one or more received instruction sets sent from the second device to the first device until they can be interleaved with other instruction set transmissions from the third device to the first device. May include buffering and / or queuing. Any well known buffering / queuing structure can be employed for this function in the improved SAS expander.

In the following, the other of the second or third device may interleave the indication frame received from the second or third device for application to the first device through the enhanced port while transmitting the current indication frame to the first device. A brief description of example processing of the interleaver to calibrate and a description of an instruction set of an exemplary, generic SAS protocol are provided. Those skilled in the art will readily appreciate that not only specific example processing is required to describe the required processing for a particular set of instructions. Rather, the example processing is a typical processing that may or may not be useful for interleaving a set of instructions received from two different devices for an application to an improved device to maintain communication for each of the two virtual connections. Is considered. Those skilled in the art will readily appreciate the specific processing useful for the particular application of the features and aspects of the present invention. For example, certain instruction sets require queuing by the interleaver and other instruction sets can simply be discarded without loss of integrity of the virtual connection or of the data transferred over the virtual connection. Furthermore, a given queued instruction set may be sent to the improved device while maintaining the order in which the instruction set was received on the corresponding virtual connection. These design details will be apparent to those skilled in the art as a matter of design choice.

The ACK, NAK, CREDIT_BLOCKED and RRDY indication sets are part of the standard of the standard SAS handshake protocol and are expected as a response to the transmission from the first device to the second device in the first virtual connection and the other (second) virtual connections are idle. Should be sent to the first device. Since many such sets of instructions (other than CREDIT_BLOCKED) can be received in a relatively quick succession between idle periods of the second virtual connection, the same number must be queued and transmitted to the first device interleaved with the validity period of the second virtual connection. do. A queued CREDIT_BLOCKED may be sent before any queued CLOSE, but a queued ACK, NAK or RRDY indication set may be sent in any order for another queued indication set (if possible). Any queued ACK, NAK, RRDY or CREDIT_BLOCKED can be removed from the queue if the connection is closed by any mechanism.

A set of DATA, SOF, EOF, SOAF, EOAF and HARD_RESET instructions may be received indicating data frame transfer, address frame transfer and reset requests from the remote port. These sets of instructions need not be queued themselves but are interleaved to be sent back to the first device at enhanced priority.

AIP, ERROR and SATA related instruction sets are not expected to be received by the interleaver from the second or third device for transmission to the first device. Thus, no buffering or queuing of this instruction set is required by the interleaver. This set of instructions can be sent to the first device or simply discarded if another virtual connection sending to the first device is currently idle. The ERROR instruction set may optionally be queued to provide more detailed information related to the error in the previous transmission back to the first device. SATA related instruction sets are not expected and in fact SATA connections can be excluded while enhanced mode of operation is enabled.

The OPEN_ACCEPT, OPEN_REJECT, DONE, CLOSE, and BREAK instruction sets are commonly used to establish / reject and control open connections and to be queued and sent to a second device if the second virtual connection becomes idle. In general, only one of these instruction sets is received at a time and therefore typically there is no need to queue more than one of these instruction sets for transmission. Queued BREAKs should normally be sent before a set of queued DONE or CLOSE directives. A queued CLOSE should generally be sent after any queued DONE or BREAK instruction set. The queued OEPN_ACCEPT must be sent before any associated queued RRDY indication set, but the queued OPEN_REJECT need not be sent in any particular order for the other queued indication set (if any). A queued DONE must be sent before any queued CLOSE instruction set, but after any queued BREAK instruction set. Any queued BREAK, OPEN_ACCEPT, OPEN_REJECT or CLOSE may be removed from the queue if the connection is closed by any mechanism.

An ALIGN instruction set may be received but need not be queued or buffered. As in the aforementioned AIP, the ALIGN instruction set may be sent to the first device if another virtual connection transmitting to the first device is currently idle.

The BROADCAST indication set can be received at any time over the virtual connection but must be sent to the first device and therefore queued for later transmission if another virtual connection becomes idle. General processing within the SAS extender already provides queuing of such BROADCAST instruction sets, so similar queuing is used to queue the BROADCAST and then send the queued instruction set to the first device. A queued BROADCAST typically does not need to be sent in any particular order for any other queued indication set.

The NOTIFY instruction set is often sent by the device to indicate readiness for further processing (eg, spin up of a disk drive, etc.). According to the SAS protocol, they can be sent periodically in four groups and can also be replaced by the ALIGN instruction set. If this set of instructions is queued when the connection is about to be closed, then the queued NOTIFY (or ALIGN) must be sent before the connection is closed. Any queued NOTIFY can be removed from the queue if the connection is closed by any mechanism.

Those skilled in the art will appreciate any of the various queuing structures and methods to be used for such queue structures. For example, a simple bit array may be provided in which each bit represents one type of instruction set that may or may not exist in the queue when the corresponding bit is set or reset. Alternatively, a more typical queue structure having an entry list or linked list structure in the form of a pushdown list may be provided with each entry corresponding to one set of instructions to be transmitted. Such design choices will be apparent to those skilled in the art.

Furthermore, those skilled in the art will readily appreciate the logic that may be implemented to detect when other virtual connections have become idle. The SAS specification provides various states in the sample state machine model, in which a particular connection is known to be idle. This idle period may be used by another virtual low speed (via the interleaver of the improved port) to send the queued indication set back to the first device. Accordingly, certain details of the design of combination and / or sequential logic that implement the features and aspects described herein as demultiplexers of control logic, interleaver, and / or improved ports are readily apparent to those skilled in the art as a matter of design choice. Could be.

While the present invention has been illustrated and described in the drawings and the foregoing description, it should be understood that these examples and description are exemplary only, and not in a limiting sense. Other embodiments of the invention and minor variations thereof have been shown and described. Protection against all changes and modifications falling within the spirit of the invention is required. Those skilled in the art will readily recognize variations of the foregoing embodiments that fall within the scope of the invention. In particular, those skilled in the art will readily appreciate that features and aspects of the present invention may be implemented equivalently within electronic circuitry or as appropriately programmed instructions of a general purpose or dedicated processor. The equivalent and programming design of such circuits is well known to those skilled in the art as a matter of design choice. As a result, the invention is not limited to the specific examples and examples described above, but rather is limited only by the following claims and their equivalents.

Claims (20)

Three SAS devices including a first SAS device, a second SAS device, and a third SAS device; A SAS expander configured to couple the first SAS device to each of the second SAS device and the third SAS device; The first SAS device and the SAS extender simultaneously allow and operate a first open connection between the first SAS device and the second SAS device and a second open connection between the first SAS device and the third SAS device. Configured to The first open connection and the second open connection use a single physical link (PHY) to couple the first SAS device to the SAS extender. system. The method of claim 1, The first open connection is used to transmit a frame from the first SAS device to the second SAS device, The second open connection is used to send a frame from the third SAS device to the first SAS device. system. The method of claim 2, The system is configured to block a receive credit associated with the first SAS device at the first open connection by sending a CREDIT BLOCKED primitive from the first SAS device to the second SAS device. system. The method of claim 2, The system is configured to discard RRDY prototypes normally sent from the third SAS device to the first SAS device in the second open connection. system. The method of claim 1, The SAS extender is configured to reject open address frames from a fourth SAS device directed to the first SAS device while the second open connection remains open. system. The method of claim 1, The SAS extender is configured to delay an open address frame from a fourth SAS device directed to the first SAS device while the second open connection remains open. system. A method operable in a SAS domain with a SAS extender that couples a first SAS device to each of a second SAS device and a third SAS device, the method comprising: Establishing a first virtual connection between the first SAS device and the second SAS device via the SAS extender, wherein the first virtual connection is established by the first SAS device and from the first SAS device; 2 used to send frames to SAS devices-and, Establishing a second virtual connection between the first SAS device and the third SAS device via the SAS extender, wherein the second virtual connection is established by the third SAS device and from the third SAS device; 1 used to send frames to SAS devices, including The first virtual connection and the second virtual connection may overlap operations, The first virtual connection and the second virtual connection use the same physical link (PHY) to couple the first SAS device to the SAS extender. Way.  The method of claim 7, wherein  Rejecting an open address frame from a fourth SAS device directed to the first SAS device while the second open connection remains open; Way. The method of claim 7, wherein Discarding the RRDY prototype sent by the third SAS device to the first SAS device. Way. The method of claim 7, wherein Transmitting a CREDIT BLOCKED prototype from the first SAS device to the second SAS device. Way. A SAS extender configured to join a first SAS device, a second SAS device, and a third SAS device, wherein: First virtual connection logic configured to establish and operate a first virtual connection between the first SAS device and the second SAS device to transmit a frame from the first SAS device to the second SAS device; A second virtual connection logic configured to establish and operate a second virtual connection between the first SAS device and the third SAS device to transmit a frame from the third SAS device to the first SAS device; The first virtual connection logic and the second virtual connection logic operate the first virtual connection and the second virtual connection respectively using a single physical link (PHY) that connects the SAS extender to the first SAS device. Configured to allow nesting SAS extenders. The method of claim 11, Further includes open connection rejection logic configured to reject open frame requests from a fourth SAS device directed to the first SAS device while the second virtual connection remains open. SAS extenders. The method of claim 11, The second virtual connection logic further includes duplex logic configured to discard the RRDY prototype from the third SAS device to the first SAS device. SAS extenders. The method of claim 11, The first virtual connection logic further includes doubled logic configured to block incoming credit associated with the first SAS device in a first open connection by sending a CREDIT BLOCKED prototype from the first SAS device to the second SAS device. SAS extenders. The method of claim 11, The second virtual connection logic is configured to reject open address frames from a fourth SAS device directed to the first SAS device while a second open connection remains open. SAS extenders. The method of claim 11, The second virtual connection logic is configured to delay an open address frame from a fourth SAS device directed to the first SAS device while the second open connection remains open. SAS extenders. As a SAS termination device, First virtual connection logic configured to establish and operate a first virtual connection through a SAS extender between the SAS termination device and the first SAS device to transmit a frame from the SAS termination device to a first SAS device; A second virtual connection logic configured to establish and operate a second virtual connection through a SAS extender between the SAS terminator and the second SAS device to transmit a frame from a second SAS device to the SAS terminator; The first virtual connection logic and the second virtual connection logic are respectively configured to allow the first virtual connection and the second virtual connection to overlap operations; The SAS terminator is configured to establish the first virtual connection and the second virtual connection on the same physical link (PHY) that couples the SAS terminator to the SAS extender. SAS terminator. 18. The method of claim 17, The second virtual connection logic further includes doubled logic configured to discard an RRDY circle from the second SAS device to the SAS end device. SAS terminator. 18. The method of claim 17, The first virtual connection logic further includes double logic configured to block received credits associated with the first SAS device in a first open connection by sending a CREDIT BLOCKED prototype from the SAS end device to the first SAS device. SAS terminator. 18. The method of claim 17, Further comprising double logic configured to manage transmit credits associated with the first virtual connection independent of receive credits associated with the second virtual connection. SAS terminator.

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