[CentOS] puzzling md error ?

[Les Mikesell]

On 2/28/2010 6:15 PM, Stephen Harris wrote:
> On Sun, Feb 28, 2010 at 02:37:13PM -0800, John R Pierce wrote:
>> And how do I know all these mirror data mismatches are Swap?  does not
>> each mismatch mean the mirrors disagree, which means one of them is
>> wrong.  Which one?  since they aren't timestamped or checksummed (like
>
> This thread is very timely.  I updated my C5.3 to 5.4 last week (not
> sure why it took me so long) and this morning noticed my raid5 was
> resyncing.  5*1Tbyte disks.  The resync took...
>    Feb 28 04:22:02 mercury kernel: md: syncing RAID array md3
>    Feb 28 16:27:06 mercury kernel: md: md3: sync done.
>
> Performance was bad during this time.  Not terrible from an interactive
> point of view, but a job that normally run from 4am to 10am didn't finish
> until 3pm.
>
> I like the concept of checking the disks are good, but it really
> sounds like there are practical problems (false positives, performance
> degregation) .
>
> So I think /etc/sysconfig/raid-check is going to read
>    ENABLED=no

I agree that is is a fairly surprising behavior change for an 
'enterprise' system where the point is mostly to not have surprising 
behavior changes.  On the other hand it is probably a good thing to do 
if you can make the scheduling fit in.

-- 
   Les Mikesell
    lesmikesell at gmail.com