Abstract: A SAS expander includes DMD timers for each PHY so that the expander can track disconnected devices directly connected to the expander and signal a SAS controller when the DMD is exceeded. A system including such SAS expanders may reduce the load on the system controller. A controller may recognize expanders capable of tracking DMDs for backwards compatibility.

Abstract: Systems and methods presented herein provide for region lock management in an expander. In one embodiment, an expander, being operable to link a plurality of initiators to a plurality of Redundant Array of Independent Disks logical volumes, includes a plurality of physical transceivers, each being operable to link the logical volumes to the initiators, and a region lock manager operable to receive a request from a first of the initiators to lock a region of the logical volumes for an input/output operation by the first initiator. The region lock manager is also operable to determine if the requested region is unlocked, to lock the requested region from the remaining initiators to allow the input/output operation of the first initiator after determining the requested region is unlocked, and to unlock the requested region after the input/output operation of the first initiator is complete.

Abstract: Methods and structure are provided for performing a rebuild using a Serial Attached SCSI (SAS) expander. The SAS expander includes an SMP target operable to receive, from a Redundant Array of Independent Disks (RAID) controller, a Serial Management Protocol (SMP) command for initiating a rebuild of a RAID volume at the SAS expander. The SAS expander also includes a control unit operable to initiate a rebuild of the RAID volume based on the received SMP command from the controller, and a Serial SCSI Protocol (SSP) initiator operable to generate SSP commands for performing the RAID rebuild based upon input from the control unit.

Abstract: An expander for a device architecture, such as a SAS-compatible expander for a SAS architecture, is configured to follow a set of discovery rules that are applied following detection of a discovery-triggering event, such as system power up or reset. According to one of the discovery rules, the expander waits until after a specified duration following the detected discovery-triggering event before passing on, to any other expanders, any requests to check the status of their discovery processing. Using appropriate values for the specified durations for different expanders, the discovery procedure will be performed without any infinite-messaging problems, even when the device architecture has a loop.

Abstract: Methods and structure are provided for provisioning a Redundant Array of Independent Disks (RAID) volume via an expander that can be used to provision a RAID volume managed by an external RAID controller. The structure includes a Serial Attached SCSI (SAS) expander. The expander comprises physical links with transceivers (PHYs) that directly couple with storage devices, a protocol target and a control unit. The control unit provisions a first RAID volume with multiple storage devices that are directly coupled with the PHYs, and is further masks the storage devices from a SAS domain, by presenting the PHYs directly coupled with the multiple storage devices as a single PHY coupled with a single logical device. The control unit is also operable to provision a portion of a second RAID volume on the logical device in response to the expander receiving a command from a RAID controller.

Abstract: Methods and structure are provided for performing a rebuild using a Serial Attached SCSI (SAS) expander. The SAS expander includes an SMP target operable to receive, from a Redundant Array of Inexpensive Disks (RAID) controller, a Serial Management Protocol (SMP) command for initiating a rebuild of a RAID volume at the SAS expander. The SAS expander also includes a control unit operable to initiate a rebuild of the RAID volume based on the received SMP command from the controller, and a Serial SCSI Protocol (SSP) initiator operable to generate SSP commands for performing the RAID rebuild based upon input from the control unit.

Abstract: Methods and structure are provided for Serial Attached SCSI (SAS) expanders that program their own routing attributes. The structure includes a SAS expander comprising multiple physical links with associated transceivers (PHYs), wherein the PHYs are configured into ports at the expander, and a memory that defines routing attributes for each of the ports. The SAS expander also comprises a control unit that is operable to detect a discovery Serial Management Protocol (SMP) request received at a port of the expander, and that is further operable to set the routing attribute for the port to subtractive routing responsive to detecting the SMP request.

Abstract: A SAS expander includes DMD timers for each PHY so that the expander can track disconnected devices directly connected to the expander and signal a SAS controller when the DMD is exceeded. A system including such SAS expanders may reduce the load on the system controller. A controller may recognize expanders capable of tracking DMDs for backwards compatibility.