On Tue, 2007-09-25 at 10:14 -0700, Vincent Fox wrote:
> Where is ZFS with regards to the NVRAM cache present on arrays?
>
> I have a pile of 3310 with 512 megs cache, and even some 3510FC with
> 1-gig cache. It seems silly that it's going to waste. These are
> dual-controller units so I have no worry about loss of cache
> information.
I've done a few experiments with using small LUNs from a surplus 3510
raid unit for a separate intent log while putting the main body of the
pool in directly connected 3510 JBOD arrays. Seems to work well; writes
to the intent log device show a much lower asvc_t (average service time)
value in iostat than writes to the main pool disks, and NFS performance
in a few completely unscientific and uncontrolled tests that are vaguely
representative of our workload seems to be better.
The behavior I'm seeing is consistent with the 3510 raid controller
ignoring the "synchronize cache" command.
I haven't put this into production just yet.
- Bill
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