BOUNCE t10 at t10.org: Non-member submission from ["Ian Davies" <Ian.Davies at dothill.com>]

T10 Reflector Admin by way of John Lohmeyer <john.lohmeyer@lsi.com> john.lohmeyer at lsi.com
Fri Mar 2 08:16:24 PST 2007


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Subject: RE: CLEAR TASK SET task management function
Date: Thu, 1 Mar 2007 18:18:48 -0700
From: "Ian Davies" <Ian.Davies at dothill.com>
To: "Elliott, Robert \(Server Storage\)" <Elliott at hp.com>
Cc: <t10 at t10.org>
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Dot Hill external RAID controllers use the clear task set TMF for the
same reason.
=20
________________________________
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Charles
Binford
Sent: Tuesday, February 27, 2007 7:56 AM
To: Elliott, Robert (Server Storage)
Cc: t10 at t10.org
Subject: Re: CLEAR TASK SET task management function
=20
Rob - we have found Clear Task Set useful for the following scenario:=20
*	simple jbod config accessed via FC switch=20
*	commands in progress on side A, and a link goes down that gives
access to side A. =20
*	if it is the host side of the switch with the link down, the
drive doesn't know about it=20
*	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=20
*	a Clear Task Set clears up this situation=20
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:=20
=20
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.
=20
If so, would that software be happy to use one of these instead?=20
a) ABORT TASK SET - just clear tasks from the same I_T nexus; or=20
b) LOGICAL UNIT RESET - clear tasks from all I_T nexuses and wipe out
other
state information=20
=20
--
Rob Elliott, elliott at hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
https://ecardfile.com/id/RobElliott
=20
=20
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Dot Hill external RAID controllers use the clear task set TMF = for the same
reason.
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Charles
Binford
Sent: Tuesday, February = 27, 2007 7:56 AM
To: Elliott, Robert = (Server Storage)
Cc: t10 at t10.org
Subject: Re: CLEAR TASK = SET task management function
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.<=
/pre>
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 =
--
<= pre>Rob Elliott, <3d.htm>elliott at hp.com
Hewlett-Packard Industry Standard =
Server Storage Advanced =
Technology
<3d.htm>https://ecardfile.com/id/Rob=
Elliott



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