On Aug 25, 2009, at 4:43 AM, Steve Hanson wrote:
If anything I would think that FMA would make the disks spin up
from
standby state sooner due to the periodic polling above, not delay
it.
From a power management perspective, should FMA *not* poll on disks
that have been put into a standby mode?
I would think not, but maybe we could check on SMART status
without actually causing the disk to spin up?
I wouldn't have thought the MODE_SENSE to get the SMART data would
itself
need to spin up the disks. However it's possible that libdiskstatus
might
spin the disk up when opening the device. Might be worth checking
with Eric?
Reading the log pages will definitely require the disks to spin up.
This is a known issue with the disk-transport module (and it's
previous incarnation, sfx4500-disk). The long term plan is to replace
it entirely with in-band monitoring via CHECK CONDITION codes instead
of the polling mechanism. In the short term, it would not be
difficult to check the devinfo power management properties, expose
that through libtopo, and skip those disks that are powered down.
- Eric
--
Eric Schrock, Fishworks http://blogs.sun.com/eschrock
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