On Fri, Mar 22, 2013 at 12:46 PM, Arnold Krille <arnold AT arnoldarts DOT de> 
wrote:
> Actually I am in the same position and working my way trough lots of
> interesting-configured machines and legacy stuff (to say it nicely).
>
> But blaming the data-loss on the software-raid and not on the missing
> monitoring/care, is just plain wrong.

Yes, md raid is somewhat sensitive to timing/soft-errors and will kick
redundant members out where running the disk running natively or as
the last mirror instance might succeed because it will retry more
aggressively.  And once it is kicked out, it won't ever re-sync
itself.    I've had some problems with aging SCSI controllers and with
'green' SATA drives that like to sleep causing mirrors to break.   But
the point of having the mirror is that drives are expected to fail and
if you don't ever check the mirroring, they will both eventually fail.
 In fact it is fairly critical to catch this quickly, because an
unreadable sector on the remaining partition (which won't be
immediately obvious but is likely if the drives are the same age) will
prevent a successful re-sync.

These days most drives are 'smart' compatible - and your OS may even
try to email notifications about expected issues.  And in any case a
simple 'cat /proc/mdstat' once in a while will show whether the
mirrors are alive.

-- 
   Les Mikesell
     lesmikesell AT gmail DOT com

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