Behavior of TEST UNIT READY command in idle and standby power conditions

Gerry Houlder gerry.houlder at seagate.com
Tue Nov 27 14:36:47 PST 2012


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1211277_f.htm">HTML-formatted message</a>

Thanks for the replies so far, but I am having a hard time interpreting
them as favoring either:
(1) TUR should complete with GOOD status (act as if the command can be
processed in idle and standby condition), or
(2) TUR should complete with CHECK CONDITION status and some flavor of NOT
READY (depending on mode page settings).
Please state preferred behavior.
On Tue, Nov 27, 2012 at 3:40 PM, <Kevin_Marks at dell.com> wrote:
> Not sure I agree Gerry.  ****
>
> ** **
>
> The description in the TUR command says “If the logical unit is able to
> accept an appropriate medium-access command without****
>
> returning CHECK CONDITION status, this command shall return a GOOD status.
> If the logical unit is unable to become operational or is in a state such
> that an application client action (e.g., START UNIT command) is required to
> make the logical unit ready, the command shall be terminated with CHECK
> CONDITION status, with the sense key set to NOT READY.” ****
>
> ** **
>
> The only defined states where this is not the case is Stopped state or any
> _wait state coming from stopped (and that was a legacy behavior). ****
>
> ** **
>
> It’s all in the state machines.****
>
> ** **
>
> Kevin****
>
> ** **
>
> ** **
>
> *From:* owner-t10 at t10.org [mailto:owner-t10 at t10.org] *On Behalf Of *Gerry
> Houlder
> *Sent:* Tuesday, November 27, 2012 9:27 AM
> *To:* T10 Reflector
> *Subject:* Behavior of TEST UNIT READY command in idle and standby power
> conditions****
>
> ** **
>
> Some questions have come up about the behavior of TEST UNIT READY command
> when the target is in an idle or standby power condition.****
>
> ** **
>
> One opinion is that TUR should be treated as a command that can be
> processed in idle and standby power conditions, so therefore should
> complete with GOOD status.****
>
> ** **
>
> Another opinion is that TUR should respond with CHECK CONDITION status
> with sense bytes indicating the target is in a low power condition and the
> target should not attempt  to change to a higher power condition. (Read or
> write commands would trigger the target to change to active power
> condition, so TUR action would be different). The advantage of this
> behavior is that it could be used to poll for low power conditions in lieu
> of using REQUEST SENSE command.****
>
> ** **
>
> The existing description of TUR command in SPC-4 rev. 36e doesn't address
> the expected behavior for this case, other than the table of "preferred TUR
> responses" doesn't include any of the low power condition sense
> combinations. However, folks can argue that there are a lot of other
> combinations that are not included there but should be reported if the
> conditions are present.****
>
> ** **
>
> I would like to see responses on the reflector for the preferred behavior
> of TUR when in a low power condition. If there is a convergence of opinion,
> i would like to have that opinion reflected in description of the TEST UNIT
> READY command to avoid having to readdress this issue in the future.****
>
> ** **
>



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