In addition, if you need the flexibility of moving disks around until
the device removal CR integrates, then mirrored pools are more flexible.
Detaching disks from a mirror isn't ideal but if you absolutely have
to reuse a disk temporarily then go with mirrors. See the output below.
You can replace disks in either configuration if you want to switch
smaller disks with larger disks, for example.
Cindy
# zpool status rzpool
pool: rzpool
state: ONLINE
scrub: resilver completed after 0h0m with 0 errors on Tue Sep 15
14:41:24 2009
config:
NAME STATE READ WRITE CKSUM
rzpool ONLINE 0 0 0
raidz2 ONLINE 0 0 0
c2t0d0 ONLINE 0 0 0
c2t2d0 ONLINE 0 0 0
c2t4d0 ONLINE 0 0 0
c2t5d0 ONLINE 0 0 0
c2t6d0 ONLINE 0 0 0
spares
c2t7d0 AVAIL
errors: No known data errors
# zpool detach rzpool c2t6d0
cannot detach c2t6d0: only applicable to mirror and replacing vdevs
# zpool destroy rzpool
# zpool create mirpool mirror c2t0d0 c2t2d0 mirror c2t4d0 c2t6d0 spare
c2t5d0
# zpool status mirpool
pool: mirpool
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
mirpool ONLINE 0 0 0
mirror ONLINE 0 0 0
c2t0d0 ONLINE 0 0 0
c2t2d0 ONLINE 0 0 0
mirror ONLINE 0 0 0
c2t4d0 ONLINE 0 0 0
c2t6d0 ONLINE 0 0 0
spares
c2t5d0 AVAIL
errors: No known data errors
# zpool detach mirpool c2t6d0
#
On 09/16/09 08:31, Edward Ned Harvey wrote:
Hi. If I am using slightly more reliable SAS drives versus SATA, SSDs
for both L2Arc and ZIL and lots of RAM, will a mirrored pool of say 24
disks hold any significant advantages over a RAIDZ pool?
Generally speaking, striping mirrors will be faster than raidz or raidz2,
but it will require a higher number of disks and therefore higher cost to
get the same usable space. The main reason to use raidz or raidz2 instead
of striping mirrors would be to keep the cost down, or to get higher usable
space out of a fixed number of drives.
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