Abstract: Methods and structure for preemptively terminating Serial Attached Small Computer System Interface connections are provided. One exemplary embodiment includes an expander comprising multiple physical links, switching circuitry able to establish connections between end devices coupled with the expander through the physical links, and a connection manager. The connection manager is able to process an Open Address Frame from an end device, and to determine that the Open Address Frame requests a connection through a physical link that is already servicing an established connection. The connection manager is further able to determine that the Open Address Frame requests a higher priority connection than the established connection, and to direct one of the end devices utilizing the established connection to terminate the established connection based on the higher priority.

Abstract: Systems and methods herein provide for managing devices through a Serial Attached Small Computer System Interface (SAS) expander. The SAS expander includes a processor adapted to detect deadlock conditions in a SAS environment. In one embodiment, the SAS expander is operable to detect an Open Address Frame associated with a connection request from a source device to a destination device. The Open Address Frame includes a source address and a destination address associated with the source device and the destination device, respectively. The expander receives an arbitration in progress status on a partial pathway that is associated with the connection request. The expander is further operable to modify the Open Address Frame to include a deadlock indicator and forward the modified Open Address Frame on the partial pathway. When the modified Open Address Frame is received, the expander initiates pathway recovery upon determination that the deadlock indicator is valid.

Abstract: Methods and systems are provided for enhanced link utilization in attached SCSI (SAS) topologies. A SAS expander may be configured to monitor link utilization within a SAS topology, and may manage connection requests received thereby based on the monitoring of link utilization. The monitoring may comprise determining availability of links for at least one node within the SAS topology with respect to other nodes in the SAS topology. This may be done based on pending connection requests, and/or responses thereto received by the SAS expander. It may also be done based on shared link utilization data. The managing may comprise determining for each received connection request when link unavailability in other nodes within the SAS topology prevents connectivity to a destination node corresponding to the connection request. When this situation occurs, the SAS expander may handle the connection request directly.

Abstract: A method, apparatus, and system for switching from an existing target end device to a next target end device in a multi-expander storage topology by using Fast Context Switching. The method enhances Fast Context Switching by allowing Fast Context Switching to reuse or extend part of an existing connection path to an end device directly attached to a remote expander. The method can include reusing or extending at least a partial path of an established connection between an initiator and the existing target end device for a connection between the initiator and the next target end device, whereby the existing target end device and the next target end device are locally attached to different expanders.

Abstract: Methods and systems are provided for enhanced link utilization in attached SCSI (SAS) topologies. A SAS expander may be configured to monitor link utilization within a SAS topology, and may manage connection requests received thereby based on the monitoring of link utilization. The monitoring may comprise determining availability of links for at least one node within the SAS topology with respect to other nodes in the SAS topology. This may be done based on pending connection requests, and/or responses thereto received by the SAS expander. It may also be done based on shared link utilization data. The managing may comprise determining for each received connection request when link unavailability in other nodes within the SAS topology prevents connectivity to a destination node corresponding to the connection request. When this situation occurs, the SAS expander may handle the connection request directly.

Abstract: A method, apparatus, and system for switching from an existing target end device to a next target end device in a multi-expander storage topology by using Fast Context Switching. The method enhances Fast Context Switching by allowing Fast Context Switching to reuse or extend part of an existing connection path to an end device directly attached to a remote expander. The method can include reusing or extending at least a partial path of an established connection between an initiator and the existing target end device for a connection between the initiator and the next target end device, whereby the existing target end device and the next target end device are locally attached to different expanders.

Abstract: A method of priority based connection arbitration in a SAS topology is disclosed introducing a PRIORITY field to an SAS open Address Frame (OAF). As the expander arbitrates the multiple OAFs in competition for an Expander Link, it compares the PRIORITY fields of the arbitrating OAFs. The OAF with highest value of PRIORITY is awarded the destination connection path. In case of equal PRIORITY, the next arbitration is based on the value of Arbitration Wait Time (AWT). This priority based arbitration ensures high availability of SAS connection links to the SAS targets with high priority OAFs which in turn will lead to better quality of service for those SAS targets. PRIORITY field in the OAF is set by the SAS targets based on the current OAF priority and also set by directly attached SAS storage expanders through a modification of the OAF during transit through the expander.

Abstract: Methods and apparatus for enabling Fast Context Switching (FCS) operation of an enhanced Serial Attached SCSI (SAS) expander and initiator for switching between one or more concurrently established connections including at least one Serial Advanced Technology Attachment (SATA) target device connection. Features and aspects hereof provide for enhanced logic within a SAS expander and/or initiator to detect the completion of an exchange over a first connection between an initiator device and a SATA target device and to allow switching to another (a second) connection without closing the first connection.

Abstract: Systems and methods herein provide for managing connection requests through a Serial Attached Small Computer System Interface (SAS) expander. In one embodiment, the expander receives a low priority open address frame (OAF) that includes a source address and a destination address. The expander also receives a high priority OAF that includes a source address and a destination address. The high priority OAF requires at least a portion of a partial path acquired by the low priority OAF for which connection request arbitration is in progress. The expander determines whether the high OAF source address matches the low OAF destination address, and in response to a determination that the high OAF source address is different than the low OAF destination address, acquires pathway resources from the low priority OAF and forwards the high priority OAF in accordance with its destination address.

Abstract: Systems and methods herein provide for managing devices through a Serial Attached Small Computer System Interface (SAS) expander. The SAS expander includes a processor adapted to detect deadlock conditions in a SAS environment. In one embodiment, the SAS expander is operable to detect an Open Address Frame associated with a connection request from a source device to a destination device. The Open Address Frame includes a source address and a destination address associated with the source device and the destination device, respectively. The expander receives an arbitration in progress status on a partial pathway that is associated with the connection request. The expander is further operable to modify the Open Address Frame to include a deadlock indicator and forward the modified Open Address Frame on the partial pathway. When the modified Open Address Frame is received, the expander initiates pathway recovery upon determination that the deadlock indicator is valid.

Abstract: Methods and structure for preemptively terminating Serial Attached Small Computer System Interface connections are provided. One exemplary embodiment includes an expander comprising multiple physical links, switching circuitry able to establish connections between end devices coupled with the expander through the physical links, and a connection manager. The connection manager is able to process an Open Address Frame from an end device, and to determine that the Open Address Frame requests a connection through a physical link that is already servicing an established connection. The connection manager is further able to determine that the Open Address Frame requests a higher priority connection than the established connection, and to direct one of the end devices utilizing the established connection to terminate the established connection based on the higher priority.

Abstract: A method of priority based connection arbitration in a SAS topology is disclosed introducing a PRIORITY field to an SAS open Address Frame (OAF). As the expander arbitrates the multiple OAFs in competition for an Expander Link, it compares the PRIORITY fields of the arbitrating OAFs. The OAF with highest value of PRIORITY is awarded the destination connection path. In case of equal PRIORITY, the next arbitration is based on the value of Arbitration Wait Time (AWT). This priority based arbitration ensures high availability of SAS connection links to the SAS targets with high priority OAFs which in turn will lead to better quality of service for those SAS targets. PRIORITY field in the OAF is set by the SAS targets based on the current OAF priority and also set by directly attached SAS storage expanders through a modification of the OAF during transit through the expander.

Abstract: An algorithm that maintains the symmetry of a symmetric bit matrix stored in computer memory without having to process all of the elements of a transpose column by considering only the elements changed in a row. The algorithm operates on groups of bits forming rows of the matrix rather than processing the individual bit elements of the matrix. Instead of checking whether each bit needs to be modified, the algorithm toggles only the column bits that are the transpose elements of modified row elements, thereby taking advantage of the existing symmetry to eliminate unnecessary conditional operations. As a result, the algorithm modifies the matrix on a row-by-row basis and makes changes to only those column bits that correspond to modified row elements without having to check the value of the transpose column elements that do not require modification.

Abstract: A method, apparatus, and system for switching from an existing target end device to a next target end device in a multi-expander storage topology by using Fast Context Switching. The method enhances Fast Context Switching by allowing Fast Context Switching to reuse or extend part of an existing connection path to an end device directly attached to a remote expander. The method can include reusing or extending at least a partial path of an established connection between an initiator and the existing target end device for a connection between the initiator and the next target end device, whereby the existing target end device and the next target end device are locally attached to different expanders.

Abstract: Methods and apparatus for enabling Fast Context Switching (FCS) operation of an enhanced Serial Attached SCSI (SAS) expander and initiator for switching between one or more concurrently established connections including at least one Serial Advanced Technology Attachment (SATA) target device connection. Features and aspects hereof provide for enhanced logic within a SAS expander and/or initiator to detect the completion of an exchange over a first connection between an initiator device and a SATA target device and to allow switching to another (a second) connection without closing the first connection.

Abstract: A method for broadcast forwarding in a SAS topology having a zoned portion of a service delivery system (ZPSDS) is disclosed. The ZPSDS includes at least a first zoning expander and a second zoning expander. The method includes originating a broadcast primitive on the first zoning expander; forwarding solely the broadcast primitive to the second zoning expander from the first zoning expander; initiating a discovery process from the second zoning expander upon receiving the broadcast primitive; and generating a source zone group list upon completion of the discovery process.