SAT TEST UNIT READY command translation

Pat LaVarre plavarre at lexar.com
Mon Aug 15 16:38:00 PDT 2005


* From the T10 Reflector (t10 at t10.org), posted by:
* "Pat LaVarre" <plavarre at lexar.com>
*
The SCSI drives of my experience vary.

a) With some SCSI models, yes, as you describe, the SCSI op 00h "TEST
UNIT READY" while stopped does provoke the h 02 04 02 "LOGICAL UNIT NOT
READY" "INITIALIZING COMMAND REQUIRED" message back.

b) Other SCSI models respond instead with h 02 04 00 Cause Not
Reportable.

c) Other SCSI models respond instead automagically entering the active
state, as you describe for ATA.

Last I checked, the most massively distributed operating systems
timed-out, reset, and retried with variable reliability unless the PDT
00h drive could implement alternative (c) with no more than a few
seconds delay.  Delays as small as three seconds caused some trouble,
delays as large as fifteen seconds caused much trouble.

-----Original Message-----
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of
Sheffield, Robert L
Sent: Monday, August 15, 2005 11:56 AM
To: t10 at t10.org
Subject: RE: SAT TEST UNIT READY command translation
...

There is a basic problem here - ATA drives do not support the equivalent
of the SCSI "STOPPED" state.
The current definition of TEST UNIT READY in SAT assumes the ATA STANDBY
state is the equivalent of the SCSI STOPPED state. But, in fact, it is
not because a media access command issued to the drive will cause the
drive to enter the ACTIVE state and the command will execute
successfully, although with added latency required to transition from
the ATA STANDBY state to the ATA ACTIVE state. Whereas when a SCSI drive
is in the STOPPED state, a media access command will cause a CHECK
CONDITION status with a sense key set to NOT READY and the additional
sense code set to LOGICAL UNIT NOT READY INIITIALIZING COMMAND REQUIRED
...	


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