Patent Grant
8244948
The present disclosure generally relates to the field of Serial Attached SCSI, and more particularly to a system, method, and product for combining multiple SAS expanders into a SAS switch.
Serial Attached SCSI (SAS) is a term referring to various technologies designed to implement data transfer between computer devices. The SAS protocol is a serial successor to the parallel Small Computer System Interface. In the SAS protocol, all SAS devices are either an initiator device, a target device, or an expander device. Initiator devices are devices that begin an SAS data transfer, while target devices are the devices to which initiator devices transfer data. Together, initiator devices and target devices are known as end devices.
SAS expanders are devices that facilitate data transfer between multiple initiator devices and multiple target devices. The SAS protocol utilizes a point-to-point bus topology. Therefore, if an initiator device is required to connect to multiple target devices, a direct connection must be made between the initiator device and each individual target device in order to facilitate each individual data transfer between the initiator device and each individual target device. SAS expanders manage the connections and data transfer between multiple initiator devices and multiple target devices. SAS expanders may contain SAS devices.
A SAS switch may include, but is not limited to: at least two SAS expanders, a first SAS expander including at least two phys; a second SAS expander including at least two phys; a first SAS wide port including at least two lanes, one of the at least two lanes of the first SAS wide port designateable as a connection request lane; and a second SAS wide port including at least two lanes, one of the at least two lanes of the second SAS wide port designateable as a connection request lane, wherein the connection request lane of each SAS wide port is operably coupled to a different SAS expander of the at least two SAS expanders.
A method for combining multiple SAS expanders into a SAS switch, may include, but is not limited to: grouping a first SAS expander including at least two phys with at least a second SAS expander including at least two phys into at least a first common wide port, wherein the first common wide port includes at least two lanes; grouping the first SAS expander with at least the second SAS expander into at least a second common SAS wide port, wherein the second common wide port includes at least two lanes, wherein one of the at least two lanes of the first SAS wide port is designateable as a connection request lane, wherein one of the at least two lanes of the second SAS wide port is designateable as a connection request lane; and operably coupling the connection request lane of each SAS wide port to a different expander.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the present disclosure. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate subject matter of the disclosure. Together, the descriptions and the drawings serve to explain the principles of the disclosure.
The numerous advantages of the disclosure may be better understood by those skilled in the art by reference to the accompanying figures in which:
Reference will now be made in detail to the subject matter disclosed, which is illustrated in the accompanying drawings.
A SAS topology featuring a single, cohesive SAS expander in accordance with an exemplary embodiment of the present disclosure is shown. The topology 100 may include initiator 110 connected to expander 120 via narrow ports 115a . . . d. Expander 120 may be connected to single, cohesive SAS expander 200 via narrow ports 125a . . . d. Single, cohesive SAS expander 200 may contain a plurality of physically separate SAS expanders 202a . . . d. SAS expanders 202a . . . d may be configured to share an identical SAS address to combine narrow ports 125a . . . d to behave as single common wide port 150. As shown in SAS topology 100, narrow ports 125a . . . d may combine to make x4-wide port 150. SAS expanders 202a . . . d may be connected to expander 130 via narrow ports 135a . . . d. Expander 130 may be connected to target 140 via narrow ports 145a . . . d. SAS specifications require that all connections be point-to-point. However, SAS topology 100 is SAS specification compliant because wide port 150 is a true SAS wide port.
Referring to
Output ports 205-244 may be wide ports. Output ports 205-244 may be configured to share an identical SAS address. Under SAS specifications, this defines output ports 205-244 to be a single wide port of the same expander. Each of output ports 205-244 may be connected to every SAS expander 202a . . . h (Not shown). The width of output ports 205-244 may depend on how many SAS expander ports are used in links 255a . . . h-294a . . . h to connect to each of output ports 205-244. Each of SAS expander 202a . . . h may have multiple SAS expander ports connected to each of output ports 205-244. For example, if single, cohesive SAS expander 200 contains two SAS expanders 202a-h connected to each of output ports 205-244 via links 255a . . . h-294a . . . h using one SAS expander port, then output ports 205-244 will be a x2 wide port. Furthermore, if single, cohesive SAS expander 200 contains two SAS expanders 202a-h connected to each of output ports 205-244 via links 255a . . . h-294a . . . h using two SAS expander ports, then output ports 205-244 will be a x4 wide port. These configurations may allow for simultaneous access of any port to any other port of single, cohesive SAS expander 200 at full port bandwidth.
A blade center switch configuration 301 of single, cohesive SAS expander 300 is provided. Referring to
SAS expanders 202a . . . h may be configured to share an identical SAS address. Under SAS specifications, this defines SAS expanders 202a . . . h to be a single expander. Firmware may run on each of SAS expanders 202a . . . h so SAS expanders 202a . . . h behave and respond as a single expander. As shown in
Referring generally to
The method 600 may further include the step of assigning an identical SAS address to the first SAS expander and the second SAS expander 604. Assigning an identical SAS address to the first SAS expander and the second SAS expander may allow the first SAS expander and the second SAS expander to behave and respond as a single, cohesive SAS expander 200. The assigning may be performed via firmware executing on the first SAS expander and the second SAS expander. Further, the phy numbering of the first SAS expander and the second SAS expander may be remapped to appear as a single, logically ordered phy numbering of a single, cohesive SAS expander. For example, a first numbered phy of the first SAS expander may be remapped to be in a first range of the single, logically ordered numbering and a second numbered phy of the second SAS expander may be remapped to be in a second range of the single, logically ordered numbering.
The method 600 may further include the step of connecting the first SAS expander directly to the second SAS expander for inter-expander communications 606. The inter-expander communications may utilize SMP communications or other communication methods, such as Inter-Integrated Circuit Bus Protocol (I2C), Enhanced Parallel Port (EPP), Ethernet, shared memory, and the like. In additional embodiments, the connection between the first SAS expander and the second SAS for inter-expander communications (430-435) may be performed via the phys of the first SAS expander and the phys of the second SAS expander. Further, the phys of the first SAS expander for inter-expander communications and the phys of the second SAS expander for inter-expander communications may be hidden from the primary switched domain (410) of the single, cohesive SAS expander. At least two phys of the first SAS expander and at least two phys of the second SAS expander may be used for inter-expander communications between the first SAS expander and the second SAS expander. Further, if at least one SAS expander within the single, cohesive SAS expander remains operational (ex.—such as during an SAS expander failure), all common SAS wide ports remain operational, with all common SAS wide ports operating at a reduced bandwidth.
The single, cohesive SAS expander 500 may be configured to provide path failover when an internal link fails within the single, cohesive SAS expander. Referring to
The data transfer intended to be transmitted via failed link 566b may be re-routed to another SAS expander connected to output port 516. This data transfer may be re-routed to another SAS expander via the phys used for inter-expander communications between the SAS expanders. As shown in single, cohesive SAS expander 500, the data transfer between SAS expander 202c and output port 516 via failed link 566b may be re-routed through SAS expander 202d via inter-expander communications link 434. From SAS expander 202d, the data transfer may be re-routed to output port 516 via link 566c. Thus output port 516 may receive the data transfer as originally intended, but may receive the data transfer on a different phy. Further, if SAS expander 202d already has an active link to output port 516, SAS expander 202c may respond to the SAS initiator with an arbitration in progress (AlP), as provided via SMP. The SAS initiator may attempt the data transfer at a later time after receiving an AlP or OPEN REJECT (RETRY) SMP response from SAS expander 202c.
In a further aspect of the present disclosure, firmware executing on the SAS expanders may reprogram the SAS expander route tables to re-route connections through inter-expander communications links (430-435) instead of through the failed links. Further, a SAS initiator connected to the single, cohesive SAS expander may learn that link 566b has failed by receiving a CHANGE primitive. For example, SMP provides a CHANGE primitive. The SAS initiator may then perform a SAS Discovery, for example, as provided via SMP. Further, the SAS initiator may note the number of remaining active connections to the target, and may only initiate a number of simultaneous data transfers equal to the number of remaining active connections to the target.
Referring generally to
The method 700 may further include the step of re-routing a data transfer of the first SAS expander connected to the device via the failed link to a second SAS expander connected to the device via a functional link 704. For example, the failed link of the single, cohesive SAS expander may fail due to a physical problem within the failed link. In another example, the failed link may fail due to a logical problem. The first SAS expander may be connected to the second SAS expander via the phys of the first SAS expander and the phys of the second SAS expander for inter-expander communications. In further embodiments, the re-routing a data transfer of a SAS expander connected to a device via the failed link to a second SAS expander connected to the device via the functional link may occur via the phys of the first expander for inter-expander communications and the phys of the second SAS expander for inter-expander communications. In exemplary embodiments, the re-routing a data transfer may include reprogramming a route table of the first SAS expander to re-route the data transfer from the failed internal link to the links between via the phys of the first expander for inter-expander communications and the phys of the second SAS expander for inter-expander communications. For example, the reprogramming of the route table of the first SAS expander may be performed via firmware executing on the first SAS expander.
The step of re-routing data transfers from a failed link within the single, cohesive SAS expander to a second SAS expander via a link for inter-expander communications may not indicate to SAS initiators and SAS targets connected to the single, cohesive SAS expander that such re-routing is occurring. However, if the second SAS expander currently has an active link to the device and data is re-routed from the failed link to the second SAS expander, the first SAS expander connected to the device via the failed link may respond with an AlP response. In such a case, a SAS initiator receiving the AlP response may retry the data transfer at a later time. A SAS initiator connected to the single, cohesive SAS expander may be notified of the failed link via receiving a CHANGE primitive. Upon receiving a CHANGE primitive, the SAS initiator may perform a SAS Discovery. For example, SMP provides a SAS Discovery, which includes a SAS Discover and a SAS Discover response.
A SAS-initiator specified data connection configuration 800 is provided. Referring to
SAS initiator 810 may specify the lanes of wide ports 880, 890 to be used to create a data connection from SAS initiator 810 to one of SAS targets 850-875. Specifying the lanes of wide ports 880, 890, may be used for fairness control, where some lanes of wide ports 880, 890 may be used to access SAS targets 850-875 and other lanes of wide ports 880, 890 may be used to pass through to other parts of a SAS configuration. SAS initiator 810 may further specify the lanes within an OPEN frame of a connection request. Such an OPEN frame may be provided via an SMP connection request. SAS initiator 810 may have learned the optimal lanes for a data connection from SAS initiator 810 to one of SAS targets 850-875 via a performing a standard SAS discovery process. SAS expander 830 and SAS expander 840, along with SAS targets 850-875 may be configured to respond via the SMP Discover response with the optimal lanes for a data connection from SAS initiator 810 to one of SAS targets 850-875. Each SAS expander in the data connection between SAS initiator 810 and one of SAS targets 850-875 may check the OPEN frame of the connection request from SAS initiator 810 for the allowed lanes for the data connection and only makes a data connection on those specified lanes.
Referring generally to
The method 900 may further include the step of specifying the allowable lanes for the data connection within the SAS wide ports of each level of the SAS domain 904. For example, the allowable lanes for the data connection may be specified via a SAS initiator connection request. The allowable lanes for the data connection may further be specified within an OPEN frame of a SAS initiator connection request.
The method 900 may further include the step of checking for the specified allowable lanes for the data connection 906. For example, when a SAS expander (820-840) receives an OPEN frame of a SAS initiator connection request, the SAS expander may check the OPEN frame for the specified allowable lanes for the data connection.
The method 900 may further include the step of creating the data connection of the specified allowable lanes 908. For example, a SAS expander may create the data connection on the specified allowable lanes. Further, the SAS expander may create the data connection after checking the OPEN frame of a SAS initiator connection request for the specified allowable lanes.
A SAS switch implementation 1000 is provided in the current disclosure. Referring generally to
SAS expanders 1030-1036 may be operably coupled to output connector 1060 via links 1080, 1090. Each of links 1080, 1090 may be operably coupled to single lanes 0-3 of output connector 1060. SAS switch 1010 may access SAS target 1070 via output connector 1060. Lanes 0-3 of output connector 1060 may operate as SAS wide ports for SAS switch 1010. As shown in
Single lane 0-3 of input connectors 1040-1046 may be designateable as connection request lanes for input connectors 1040-1046. For example, SAS initiators 1020-1026 may send a SAS OPEN request command over lane 0 of input connectors 1040-1046. In another embodiment, a lane of input connectors 1040-1046 may be designateable as a connection request lane by SAS switch 1010. For example, SAS expanders 1030-1036 may execute firmware to designate a lane of input connectors 1040-1046 as a connection request lane. As shown in
As shown in the disclosure above and not limited to
Referring generally to
In exemplary embodiments, the method 1100 may further include the step of operably coupling the connection request lane of each SAS wide port to a different expander 1130. Each SAS wide port may be operably coupled to each SAS expander via at least one lane of the each SAS wide port. In addition, the first SAS expander and the second SAS expander may each run firmware to coordinate SAS switch operations. The first SAS expander and the second SAS expander may be operably coupled to the second SAS expander for inter-expander communications.
In the present disclosure, the methods disclosed may be implemented as sets of instructions or software readable by a device. Such software may a computer program product which employs a computer-readable storage medium including stored computer code which is used to program a computer to perform the disclosed function and process of the present invention. The computer-readable medium may include, but is not limited to, any type of conventional floppy disk, optical disk, CD-ROM, magnetic disk, hard disk drive, magneto-optical disk, ROM, RAM, EPROM, EEPROM, magnetic or optical card, or any other suitable media for storing electronic instructions. Further, it is understood that the specific order or hierarchy of steps in the methods disclosed are examples of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the method can be rearranged while remaining within the disclosed subject matter. The accompanying method claims present elements of the various steps in a sample order, and are not necessarily meant to be limited to the specific order or hierarchy presented.
It is believed that the present disclosure and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely explanatory, and it is the intention of the following claims to encompass and include such changes.
The present application claims priority from the following copending U.S. patent applications and is a continuation-in-part of copending U.S. patent application Ser. No. 12/384,289 titled, “COMBINING MULTIPLE SAS EXPANDERS TO PROVIDE SINGLE SAS EXPANDER FUNCTIONALITY”, filed Apr. 2, 2009; copending U.S. patent application Ser. No. 12/384,291 titled, “METHOD FOR PROVIDING PATH FAILOVER FOR MULTIPLE SAS EXPANDERS OPERATING AS A SINGLE SAS EXPANDER”, filed Apr. 2, 2009; and copending U.S. patent application Ser. No. 12/384,287 titled, “SPECIFYING LANES FOR SAS WIDE PORT CONNECTIONS”, filed Apr. 2, 2009; all of which, along with the present application, claim the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Ser. No. 61/191,037, filed Sep. 5, 2008. All of these applications are incorporated herein by reference.
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