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Bug#682233: (no subject)

I think this commit is somehow related to that problem:

commit 14216561e164671ce147458653b1fea06a4ada1e
Author: James Bottomley <JBottomley@Parallels.com>
Date:   Wed Jul 25 23:55:55 2012 +0400

    [SCSI] Fix 'Device not ready' issue on mpt2sas

    This is a particularly nasty SCSI ATA Translation Layer (SATL) problem.

    SAT-2 says (section 8.12.2)

            if the device is in the stopped state as the result of
            processing a START STOP UNIT command (see 9.11), then the SATL
shall terminate the TEST UNIT READY command with CHECK CONDITION
            status with the sense key set to NOT READY and the additional

mpt2sas internal SATL seems to implement this. The result is very confusing standby behaviour (using hdparm -y). If you suspend a drive and then send another command, usually it wakes up. However, if the next command is a TEST UNIT READY, the SATL sees that the drive is suspended and proceeds to follow the SATL rules for this, returning NOT READY to all subsequent commands. This means that the ordering of TEST UNIT READY is crucial: if you send TUR and then a command, you get a NOT READY to both back. If you send a command and then a TUR, you get GOOD status because the preceeding command woke the drive.

    This bit us badly because

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