On Dec 21, 2009, at 11:56 PM, Roman Naumenko <ro...@naumenko.ca> wrote:
On Dec 21, 2009, at 4:09 PM, Michael Herf
<mbh...@gmail.com> wrote:
Anyone who's lost data this way: were you doing
weekly scrubs, or
did you find out about the simultaneous failures
after not touching
the bits for months?
Scrubbing on a routine basis is good for detecting
problems early, but
it doesn't solve the problem of a double failure
during resilver. As
the size of disks become huge the chance of a double
failure during
resilvering increases to the point of real
possibility. Due to the
amount of data, the bit error rates of the medium and
the prolonged
stress of resilvering these monsters.
For up to 1TB drives use nothing less than raidz2.
For 1TB+ drives use
raidz3. Avoid raidz vdevs larger than 7 drives,
better to have
multiple vdevs both for performance and reliability.
With 24 2.5" drive enclosures you can easily create 3
7 drive raidz3s
or 4 5 drive raidz2s with a spare for each vdev, or 2
spares and 1-2
SSD drives. Both options give 12/24 usable disk
space. 4 raidz2s give
more performance, 3 raidz3s gives more reliability.
-Ross
Hi Ross,
What about old good raid10? It's a pretty reasonable choice for
heavy loaded storages, isn't it?
I remember when I migrated raidz2 to 8xdrives raid10 the application
administrators were just really happy with the new access speed. (we
didn't use stripped raidz2 though as you are suggesting).
Raid10 provides excellent performance and if performance is a priority
then I recommend it, but I was under the impression that resiliency
was the priority, as raidz2/raidz3 provide greater resiliency for a
sacrifice in performance.
-Ross
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