On Wed, 20 Jan 2010, Brad wrote:
Can anyone recommend a optimum and redundant striped configuration
for a X4500? We'll be using it for a OLTP (Oracle) database and
will need best performance. Is it also true that the reads will be
load-balanced across the mirrors?
Is this considered a raid 1+0 configuration?
Zfs does not strictly support RAID 1+0. However, your sample command
will create a pool based on mirror vdevs which is written to in a
load-shared fashion (not striped). This type of pool is ideal for
databases since it consumes the least of those precious IOPS. With
SATA drives, you need to preserve those precious IOPS as much as
possible.
Zfs does not do striping across vdevs, but its load share approach
will write based on (roughly) a round-robin basis, but will also
prefer a less loaded vdev when under a heavy write load, or will
prefer to write to an empty vdev rather than write to an almost full
one. Due to zfs behavior, it is best to provision the full number of
disks to start with so that the disks are evenly filled and the data
is well distributed.
Reads from mirror pairs use a simple load share algorithm to select
the mirror side which does not attempt to strictly balance the reads.
This does provide more performance than one disk, but not twice the
performance.
Is it even possible to do a raid 0+1?
No.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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