RAID-5 and database servers

Robert von Bismarck robert.vonbismarck at vtx-telecom.ch
Fri Mar 12 02:56:29 CST 2010


Plenty of good advice in this thread, I might add that you'd wish to use
the maximum number of disks you can pack into your box and meet your
storage requirements, and not just a few big ones, favoring RAID-6 over
RAID-5. Usually striping a busy DB over more individual disks will yield
added performance benefits, smaller disks rebuild quicker too in case of
failure and are cheaper to replace. The increase in disks does increase
the risks of RAID failure as well, but using RAID-6 plus hotspares helps
minimizing that.
Rebuild is the most critical moment in RAID-5, especially with those
newer huge disks that take ages to rebuild. Rebuilding a busy 500Gb SATA
RAID-5 took about 8 hours, but YMMV. 
During rebuild the load is increased on all the remaining disks, and as
they usually are from the same batch as all the others, they may fail
for the same reason the first one did. I had a big RAID-5 die on me
during the rebuild phase, and that is not a happy memory. Thankfully we
had some spare drives to rebuild a new array and full backups.
If money is really no object, go buy a couple ramsan's
(http://www.ramsan.com). 



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