[CentOS] /etc/cron.weekly/99-raid-check

Ross Walker rswwalker at gmail.com
Tue Dec 1 15:09:53 UTC 2009


On Dec 1, 2009, at 9:51 AM, Farkas Levente <lfarkas at lfarkas.org> wrote:

> On 12/01/2009 02:36 PM, Thomas Harold wrote:
>> So my take on all of that is, if you see it on RAID-5 or RAID-6, you
>> should worry.  But if it's on an array with memory mapped files or  
>> swap
>> files/partitions that is RAID-1 or RAID-10, it's less of a worry.
>
> but then do we (the /etc/cron.weekly/99-raid-check) need to rebuild  
> all
> of my terrabyte raid1 arrays at all weekend? if not than imho it's a  
> bug:-(

I agree, I think the real problem is that the Linux MD RAID doesn't  
quiesce the arrays when checking the mismatch_cnt so for RAID1/10  
arrays you will see the transactions committed to one side, but not  
yet on the other. For RAID5/6 the whole stripe with parity must be  
committed atomically, so there should never be a mismatch_cnt.

There should be a way to specify arrays to be skipped during the check  
until the real problem of quiescing the arrays is fixed. Or make the  
RAID1/10 write transactions atomic like the RAID5/6 (which they should  
be in my opinion, but lowers write performance).

Maybe touch a file with the name of the array to skip in a particular  
directory somewhere and have the script check that directory for  
arrays to skip?

-Ross



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