A little story of failed raid5 (3ware 8000 series)

Artem Kuchin matrix at itlegion.ru
Mon Aug 20 23:00:05 PDT 2007

Martin Nilsson wrote:
> Artem Kuchin wrote:
>> But i don't understand how and why it happened. ONly 6 hours ago (a
>> night before)
>> all those files were backed up fine w/o any read error. And now,
>> right after replacing
>> the driver and starting rebuild it said that there are bad sectors
>> all over those file.
>> How come?
> That is what patrol read is intended to detect before it is a problem.
> In a RAID5 array the checksums are only used when reconstructing data,
> if you have a bad block in a checksum sector it will not be detected
> until a drive have failed and you try to rebuild the array,
> unfortunately at that time it is too late...
> Beware that OS software solutions like diskcheckd will not find this
> as it only reads the data, not the checksums, it must be done on the
> controller.

That exactly was i was talking about. I don't acess to individual disks
behind raid unit, so, i cannot doit. I don't know it controller 
VERIFY command does it right. If it doesm then i shoudl put it into a cron
job and do it on weekly basis. Also, it would halpfull it i could get access to
number of left reserved sector for remapping. Any idea about these two for
3ware controllers? Also, someone should mention, that while using raid MUST
do verifies often.


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