On 11/11/13 09:36, Stan Hoeppner wrote:
On 11/10/2013 2:34 PM, NeilBrown wrote:
The firmware can only relocate a sector if it reads it when it is marginal
but not yet completely lost. If a sector is not read for a long time and
during that time the media degraded beyond recovery the firmware cannot do
anything. But RAID1 can - it can get it from the other device.
But is a scrub required for this? Isn't this exactly what occurs during
normal operation with md/RAID1? I.e. a read fails with disk error, so
we grab the sector from the mirror? So what advantage is there to
scrubbing md/RAID1?
Wouldn't a check of the raid cause each member to be read in full,
therefore helping the disk to notice that the sector is marginal, and/or
the RAID layer to notice that the sector is no longer readable and
therefore read from the other member, and re-write the sector. Consider
a sector that is very rarely accessed...
Or are you suggesting that a smart command issued to the underlying
devices can solve both of those scenarios?
Regards,
Adam
--
Adam Goryachev Website Managers www.websitemanagers.com.au
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