On Mon, Jul 09, 2012 at 06:24:15PM -0400, Robert Trace wrote:

On 07/09/2012 04:45 PM, Darrick J. Wong wrote:

quoted

I suspect that /sys/devices/<bunch of sas topology here>/manage_start_stop = 0
for the SATA devices hanging off the SAS controller.

Yep, looks like you're right.  For my system:

# cat /sys/block/sd?/device/scsi_disk/*/manage_start_stop
1
1
1
1
1
0
0
0
0
0
0
0
0

Those first 5 disks are SATA disks on SATA controllers.  The last 8
disks are SATA disks on the SAS controller.

quoted

Setting that sysfs
attribute to 1 is supposed to enable the SCSI layer to send TUR when it sees
"LU not ready", as well as spin down the drives at suspend/poweroff time.

Setting it to 1 doesn't seem to have made any difference, however.

# cat /sys/block/sdm/device/scsi_disk/14\:0\:7\:0/manage_start_stop
0
# echo 1 > /sys/block/sdm/device/scsi_disk/14\:0\:7\:/manage_start_stop
# cat /sys/block/sdm/device/scsi_disk/14\:0\:7\:0/manage_start_stop
1
# hdparm -y /dev/sdm

/dev/sdm:
 issuing standby command
# hdparm -C /dev/sdm

/dev/sdm:
 drive state is:  standby
# dd if=/dev/sdm of=/dev/null bs=512 count=1
dd: reading `/dev/sdm': Input/output error
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.00117802 s, 0.0 kB/s

... and on the scsi logging side, I see the read(10) to the disk which
immediately returns "Not Ready" and the I/O failure bubbles up the
chain.  And afterwards, the disk is still asleep.

# hdparm -C /dev/sdm

/dev/sdm:
 drive state is:  standby

Also, TURs don't appear to actually wake the disk up (should they?).
The only thing I've found that'll wake the disk up is an explicit START
UNIT command.

Sorry, I misspoke, manage_start_stop=1 sends START UNIT, not TUR.  Also, it
only manages spindown/up at suspend/resume time, hence the behavior you see.
The relevant source code is sd_start_stop_device() in drivers/scsi/sd.c.

--D

-- Rob