On 18/10/2010 09:28, Habony, Zsolt wrote:
I worry about head thrashing. Though memory cache of large storage should make
the problem
Is that really something you should be worried about with all the other
software and hardware between ZFS and the actual drives ?
If that is a problem then it isn't ZFS causing it, it will just be using
the LUNs that was given to it by the SAN. An access pattern of an
application on a completely different filesystem could still mean that
you are using both LUNs in that way.
Is there a way to avoid it, or can we be sure that the problem does not exist
at all ?
Grow the existing LUN rather than adding another one.
The only way to have ZFS not stripe is to not give it devices to stripe
over. So stick with simple mirrors eg this style of configuration:
pool: builds
state: ONLINE
scan: none requested
config:
NAME STATE READ WRITE CKSUM
builds ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
c7t3d0 ONLINE 0 0 0
c8t4d0 ONLINE 0 0 0
Where in your configuration c7t3d0/c8t4d0 are your LUNs from the SAN.
Rather than this style:
pool: builds
state: ONLINE
scan: none requested
config:
NAME STATE READ WRITE CKSUM
builds ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
c7t3d0 ONLINE 0 0 0
c8t4d0 ONLINE 0 0 0
mirror-1 ONLINE 0 0 0
c7t3d0 ONLINE 0 0 0
c8t4d0 ONLINE 0 0 0
--
Darren J Moffat
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