Monish Shah wrote:
Hello,
Thanks to everyone who replied.
Dan, your suggestions (quoted below) are excellent and yes, I do want
to make this work with SSDs, as well. However, I didn't tell you one
thing. I want to compress the data on the drive. This would be
particularly important if an SSD is used, as the cost per GB is high.
This is why I wanted to put it in a zpool.
Before somebody points out that compression with increase the CPU
utilization, I'd like to mention that we have hardware accelerated
gzip compression technology already working with ZFS, so the CPU will
not be loaded.
I'm also hoping that write IOPS will improve with compression, because
more writes can be combined into a single block of storage. I don't
know enough about ZFS allocation policies to be sure, but we'll try to
run some tests.
Please share what you find. It seems counterintuitive to me that
compression
would increase iops for small-block, random workloads. But real data is
better
than intuition :-)
-- richard
It looks like, for now, the mirror disks will also have to be SSDs.
(Perhaps raidz1 will be OK, instead.) Eventually, we will look into
modifying ZFS to support the kind of asymmetric mirroring I mentioned
in the original post. The other alternative is to modify ZFS to
compress L2ARC, but that sounds much more complicated to me. Any
insights from ZFS developers would be appreciated.
Monish
----
Monish Shah
CEO, Indra Networks, Inc.
www.indranetworks.com
Use the SAS drives as l2arc for a pool on sata disks. If your l2arc
is the full size of your pool, you won't see reads from the pool
(once the cache is primed).
If you're purchasing all the gear from new, consider whether SSD in
this mode would be better than 15k sas.
--
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