SAT TEST UNIT READY command translation

Douglas Gilbert dougg at
Thu Aug 18 06:32:54 PDT 2005

* From the T10 Reflector (t10 at, posted by:
* Douglas Gilbert <dougg at>
"Sheffield, Robert L" <robert.l.sheffield at> wrote:

> This has the result that a SCSI logical unit represented by the
> SATL will never be in the STOPPED state. So, even though the SATL
> processed a START STOP UNIT command with START=0, the device as
> perceived by the SCSI application client will be in the SCSI
> STANDBY state. The response to TEST UNIT READY (assuming no
> errors) should be GOOD status.

That would be consistent.
I have made a small web page to summarize power conditions
(states) across several (draft) standards:

In the context of SAS there is another power condition (actually
two) to consider: ACTIVE_WAIT. For a SAS disk this is like the
STOPPED state. Media access commands are bounced with NOT READY:
(or more) link layer NOTIFY (ENABLE SPINUP) primitives are
required (from an initiator or an expander) to transition the
SAS disk to ACTIVE power condition. A SAS transport can also
hold a SATA disk in a state similar to ACTIVE_WAIT. So if
there is a SAT layer in a SAS enclosure/expander how will this
new state be reported and transitioned?

> Question: does this cause problems for any SCSI applications
> - that a SAT logical unit will never go into the STOPPED state?

I don't think so.

Doug Gilbert
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