Avago Technologies General IP (singapore) Pte. Ltd.

Sandisk Technologies Inc.

Lsi Corporation

Shankar More

Vidyadhar Pinglikar

Kapil Sundrani

Mandar Dattatraya Joshi

Prasad Ramchandra Kadam

An electronic device including a communication interface and a command buffer coupled to the communication interface. The communication interface is configured to receive commands from a plurality of initiator devices, and the command buffer is configured to store the commands. The electronic device further includes a command buffer management module coupled to the command buffer. The command buffer management module is configured to generate a message indicating a remaining allowed storage size associated with the command buffer. The communication interface is further configured to enable communication of the message to a particular initiator device of the plurality of initiator devices. The message may enable the particular initiator device to hold off on sending one or more other commands to the command buffer if the remaining allowed storage size fails to satisfy a threshold storage size.

Data storage device with command buffer management module and method of operating same

Methods and structure for emulating wide ports at an expander are provided. An exemplary system includes a Serial Attached Small Computer System Interface (SAS) expander. The expander includes a plurality of physical links, and a controller. The controller is able to identify a physical link coupled with a device, to generate a plurality of virtual physical links that are configured as a virtual wide port coupled with the device, and to present the virtual wide port at the expander in place of the physical link.

Wide port emulation at serial attached SCSI expanders using virtual physical links

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.

Preemptive connection switching for serial attached small computer system interface systems

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.

Deadlock detection and recovery in SAS

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.

Enhancing active link utilization in serial attached SCSI topologies

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.

Method to facilitate fast context switching for partial and extended path extension to remote expanders

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.

Methods and apparatus for fast context switching of serial advanced technology attachment in enhanced serial attached SCSI expanders

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.

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Pune, India

Shankar More