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From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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Subject: Re:  ZFS raid write performance?
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On Mon, 22 Jun 2015, kpneal@pobox.com wrote:

> Reading and writing to a raidz* requires touching all or almost all of
> the disks.
>
> Writing to a mirror requires touching all the disks. Reading from a mirror
> requires touching one disk.

Keep in mind that for the same number of disks, using mirrors results 
in more vdevs and less use of precious IOPS.  Also, using mirrors 
results in larger I/O requests since zfs blocks don't need to be 
fragmented.

Bob
-- 
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/