Am 23.12.10 19:05, schrieb Eric D. Mudama:
On Thu, Dec 23 at 11:25, Stephan Budach wrote:
Hi,
as I have learned from the discussion about which SSD to use as ZIL
drives, I stumbled across this article, that discusses short
stroking for
increasing IOPs on SAS and SATA drives:
[1]http://www.tomshardware.com/reviews/short-stroking-hdd,2157.html
Now, I am wondering if using a mirror of such 15k SAS drives would
be a
good-enough fit for a ZIL on a zpool that is mainly used for file
services
via AFP and SMB.
I'd particulary like to know, if someone has already used such a
solution
and how it has worked out.
Haven't personally used it, but the worst case steady-state IOPS of
the Vertex2 EX, from the DDRDrive presentation, is 6k IOPS assuming a
full-pack random workload.
To achieve that through SAS disks in the same workload, you'll
probably spend significantly more money and it will consume a LOT more
space and power.
According to that Tom's article, a typical 15k SAS enterprise drive is
in the 600 IOPS ballpark when short-stroked and consumes about 15W
active. Thus you're going to need ten of these devices, to equal the
"degraded" steady-state IOPS of an SSD. I just don't think the math
works out. At that point, you're probably better-off not having a
dedicated ZIL, instead of burning 10 slots and 150W.
Good - that was actually the information I have been missing. So, I will
rather go with the Vertex2 EX then and save me the hassle of short
stroking entirely.
Thanks and merry christmas to all on this list.
Cheers,
budy
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