Method to Facilitate Fast Context Switching for Partial and Extended Path Extension to Remote Expanders

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.

1 . An expander device, comprising:
 multiple physical links (PHYs); and   a processor,   wherein the expander is operable to detect that a direct-attached device has requested a new connection with an end device, to determine that the expander has a connection partially or fully established along a path of the new connection, to check if the expander has received a first DONE primitive from a direction of the new connection, and to wait for a second DONE primitive going in a direction of the new connection,   wherein in response to receiving the first DONE primitive and the second DONE primitive, the expander is further operable to convert the second DONE primitive into a DONE_SWITCH, to forward the DONE_SWITCH in the direction of the new connection, and to send a Switch Address Frame (SAF) in the direction of the new connection.   
     
     
         2 . The system of  claim 1 , wherein the direct-attached device comprises an initiator, a particular expander, or a target end device. 
     
     
         3 . The system of  claim 1 , wherein the end device comprises an initiator, a particular expander, or a target end device. 
     
     
         4 . The system of  claim 1 , wherein the SAF is configured to switch and establish the new connection. 
     
     
         5 . The system of  claim 1 , wherein:
 the expander is operable to determine that the expander has a connection partially or fully established along a path of the new connection based on a route table stored in memory.   
     
     
         6 . The system of  claim 1 , wherein:
 the expander further comprises a connection manager operable to detect receipt of the first DONE primitive.   
     
     
         7 . The system of  claim 1 , wherein:
 the expander further comprises a connection manager operable to determine that the expander has a connection partially or fully established along a path of the new connection.   
     
     
         8 . A method for initiating Fast Context Switching by an expander in a multi-expander storage topology, the method comprising:
 detecting that a direct-attached device has requested a new connection with an end device;   determining that the expander has a connection partially or fully established along a path of the new connection;   checking if the expander has received a first DONE primitive from a direction of the new connection; waiting for a second DONE primitive going in a direction of the new connection; receiving the first DONE primitive and the second DONE primitive at a same time, at approximately a same time, or at different times;   converting the second DONE primitive into a DONE_SWITCH; forwarding the DONE_SWITCH in the direction of the new connection; and   sending a Switch Address Frame (SAF) in the direction of the new connection.   
     
     
         9 . The method of  claim 8 , wherein the direct-attached device comprises an initiator, a particular expander, or a target end device. 
     
     
         10 . The method of  claim 8 , wherein the end device comprises an initiator, a particular expander, or a target end device. 
     
     
         11 . The method of  claim 8 , wherein the SAF is configured to switch and establish the new connection. 
     
     
         12 . The method of  claim 8 , further comprising:
 determining that the expander has a connection partially or fully established along a path of the new connection based on a route table stored in memory.   
     
     
         13 . The method of  claim 8 , further comprising:
 operating a connection manager of the expander to detect receipt of the first DONE primitive.   
     
     
         14 . The method of  claim 8 , wherein:
 operating a connection manager of the expander to determine that the expander has a connection partially or fully established along a path of the new connection   
     
     
         15 . A non-transitory computer readable medium embodying programmed instructions which, when executed by a processor, are operable for directing the processor to perform a method comprising:
 detecting that a direct-attached device has requested a new connection with an end device;   determining that the expander has a connection partially or fully established along a path of the new connection;   checking if the expander has received a first DONE primitive from a direction of the new connection; waiting for a second DONE primitive going in a direction of the new connection; receiving the first DONE primitive and the second DONE primitive at a same time, at approximately a same time, or at different times;   converting the second DONE primitive into a DONE_SWITCH; forwarding the DONE_SWITCH in the direction of the new connection; and   sending a Switch Address Frame (SAF) in the direction of the new connection.   
     
     
         16 . The medium of  claim 15 , wherein the direct-attached device comprises an initiator, a particular expander, or a target end device. 
     
     
         17 . The medium of  claim 15 , wherein the end device comprises an initiator, a particular expander, or a target end device. 
     
     
         18 . The medium of  claim 15 , wherein the SAF is configured to switch and establish the new connection. 
     
     
         19 . The medium of  claim 15 , wherein the method further comprises:
 determining that the expander has a connection partially or fully established along a path of the new connection based on a route table stored in memory.   
     
     
         20 . The medium of  claim 15 , wherein the method further comprises:
 operating a connection manager of the expander to detect receipt of the first DONE primitive.