CLEAR TASK SET task management function

Charles Binford Charles.Binford at Sun.COM
Tue Feb 27 06:55:57 PST 2007


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Rob - we have found Clear Task Set useful for the following scenario:
      * simple jbod config accessed via FC switch
      * commands in progress on side A, and a link goes down that gives
	access to side A.  
      * if it is the host side of the switch with the link down, the
	drive doesn't know about it
      * the host retries the commands via side B, but the drive has its
	buffer and dma resources tied up waiting for the IOs to complete
	via side A
      * a Clear Task Set clears up this situation
A LUN Reset would do the same, but it is a bigger hammer than necessary
because, as you say below it clears other state info.
cb
On Fri, 2007-02-23 at 14:50 -0600, Elliott, Robert (Server Storage)
wrote:
> Does any SCSI software other than test software actually use the CLEAR TASK
> SET task management function? CLEAR TASK SET clears tasks from all I_T
> nexuses.
> 
> If so, would that software be happy to use one of these instead? 
> a) ABORT TASK SET - just clear tasks from the same I_T nexus; or 
> b) LOGICAL UNIT RESET - clear tasks from all I_T nexuses and wipe out other
> state information 
> 
> --
> Rob Elliott, elliott at hp.com
> Hewlett-Packard Industry Standard Server Storage Advanced Technology
> https://ecardfile.com/id/RobElliott
> 
> 



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