On Dec 29, 2009, at 7:55 AM, Brad <bene...@yahoo.com> wrote:
Thanks for the suggestion!
I have heard mirrored vdevs configuration are preferred for Oracle
but whats the difference between a raidz mirrored vdev vs a raid10
setup?
A mirrored raidz provides redundancy at a steep cost to performance
and might I add a high monetary cost.
Because each write of a raidz is striped across the disks the
effective IOPS of the vdev is equal to that of a single disk. This can
be improved by utilizing multiple (smaller) raidz vdevs which are
striped, but not by mirroring them.
With raid10 each mirrored pair has the IOPS of a single drive. Since
these mirrors are typically 2 disk vdevs, you can have a lot more of
them and thus a lot more IOPS (some people talk about using 3 disk
mirrors, but it's probably just as good as getting setting copies=2 on
a regular pool of mirrors).
We have tested a zfs stripe configuration before with 15 disks and
our tester was extremely happy with the performance. After talking
to our tester, she doesn't feel comfortable with the current raidz
setup.
How many luns are you working with now? 15?
Is the storage direct attached or is it coming from a storage server
that may have the physical disks in a raid configuration already?
If direct attached, create a pool of mirrors. If it's coming from a
storage server where the disks are in a raid already, just create a
striped pool and set copies=2.
-Ross
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