On Tue, Dec 29 at 4:55, Brad 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?
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.
As a general rule of thumb, each vdev has the random performance
roughly the same as a single member of that vdev. Having six RAIDZ
vdevs in a pool should give roughly the performance as a stripe of six
bare drives, for random IO.
When you're in a workload that you expect to be bounded by random IO
performance, in ZFS you'd want to increase the number of VDEVs to be
as large as possible, which acts to distribute random work across all
of your disks. Building a pool out of 2-disk mirrors, then, is the
preferred layout for random performance, since it's the highest ratio
of disks to vdevs you can achieve (short of non-fault-tolerant
configurations).
This winds up looking similar to RAID10 in layout, in that you're
striping across a lot of disks that each consists of a mirror, though
the checksumming rules are different. Performance should also be
similar, though it's possible RAID10 may give slightly better random
read performance at the expense of some data quality guarantees, since
I don't believe RAID10 normally validates checksums on returned data
if the device didn't return an error. In normal practice, RAID10 and
a pool of mirrored vdevs should benchmark against each other within
your margin of error.
--eric
--
Eric D. Mudama
edmud...@mail.bounceswoosh.org
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