[T10] Operation of TAS bit related to Unit Attention

Bill Martin-SSI bill.martin at ssi.samsung.com
Tue Jan 26 12:08:37 PST 2016


The biggest confusion here was the apparent opposite meaning of the bit, but now it is clear that the functionality of the bit was designed in that when set to one tasks are completed with TASK ABORTED status and there is no UA. When set to zero tasks are aborted with no response to the application client and a UA issued.

Thanks,

Bill Martin
Vice Chair SNIA Technical Council
Vice Chair INCITS T10
SSD I/O Standards
Samsung Semiconductor, Inc.
Cell (408) 499-1839



From: Black, David [mailto:david.black at emc.com]
Sent: Tuesday, January 26, 2016 10:25 AM
To: Bill Martin-SSI; George.Penokie at avagotech.com; Ralph Weber (roweber at ieee.org) (roweber at ieee.org)
Cc: T10 Reflector
Subject: RE: Operation of TAS bit related to Unit Attention

I'm neither Ralph nor George, but I don' t see a serious conflict:
- The SAM-5 text is about creating a unit attention condition that is reported on a *subsequent* command (if it is reported, see SAM-5 on UA queuing behavior).
- The SPC-4 text is about how to terminate the *current* command.

It might be nice if each chunk of text acknowledged the existence of the other, but that would be editorial.  What have I missed?

Thanks, --David

From: t10-bounces at t10.org<mailto:t10-bounces at t10.org> [mailto:t10-bounces at t10.org] On Behalf Of Bill Martin-SSI
Sent: Tuesday, January 26, 2016 11:11 AM
To: George.Penokie at avagotech.com<mailto:George.Penokie at avagotech.com>; Ralph Weber (roweber at ieee.org<mailto:roweber at ieee.org>) (roweber at ieee.org<mailto:roweber at ieee.org>)
Cc: T10 Reflector; Stefanus (Fnu) Stefanus-SSI
Subject: [T10] Operation of TAS bit related to Unit Attention

Ralph & George:

There is a conflict between SAM-5 and SPC-4 on the meaning of the TAS bit.

SAM-5r21 states:
If the TAS bit is set to zero in the Control mode page (see SPC-4), then the device server creates this unit attention condition for each I_T nexus that had command(s) aborted other than the I_T nexus that delivered the command. If the TAS bit is set to one in the Control mode page (see SPC-4), then the device server does not create this unit attention condition.

SPC-4r08 states:
A task aborted status (TAS) bit set to zero specifies that aborted commands shall be terminated by the device server without any response to the application client. A TAS bit set to one specifies that commands aborted by the actions of an I_T nexus other than the I_T nexus on which the command was received shall be completed with TASK ABORTED status (see SAM-5).

Which was the intended meaning of this bit?

Thanks,

Bill Martin
Vice Chair SNIA Technical Council
Vice Chair INCITS T10
SSD I/O Standards
Samsung Semiconductor, Inc.
Cell (408) 499-1839


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