On 7 mai 09, at 04:03, Adam Leventhal wrote:
After all this discussion, I am not sure if anyone adequately
answered the
original poster's question as to whether at 2540 with SAS 15K
drives would
provide substantial synchronous write throughput improvement when
used as
a L2ARC device.
I was under the impression that the L2ARC was to speed up reads, as
it
allows things to be cached on something faster than disks (usually
MLC
SSDs). Offloading the ZIL is what handles synchronous writes, isn't
it?
How would adding an L2ARC speed up writes?
You're absolutely right. The L2ARC is for accelerating reads only
and will
not affect write performance.
With the small caveat that if the bulk of your read traffic is being
served by the L2ARC, that means there is much less contention for
access to the slower physical disks freeing them up for write
activity. No speed increase in the technical sense over and above the
capabilities of the disks, but it should have an impact in real world
IO activity.
Cheers,
Erik
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