On Wed, 18 Nov 2009, Greg Smith wrote:
Merlin Moncure wrote:
But what's up with the 400 iops measured from bonnie++?
I don't know really. SSD writes are really sensitive to block size and the
ability to chunk writes into larger chunks, so it may be that Peter has just
found the worst-case behavior and everybody else is seeing something better
than that.
When the reports I get back from people I believe are competant--Vadim,
Peter--show worst-case results that are lucky to beat RAID10, I feel I have
to dismiss the higher values reported by people who haven't been so careful.
And that's just about everybody else, which leaves me quite suspicious of the
true value of the drives. The whole thing really sets off my vendor hype
reflex, and short of someone loaning me a drive to test I'm not sure how to
get past that. The Intel drives are still just a bit too expensive to buy
one on a whim, such that I'll just toss it if the drive doesn't live up to
expectations.
keep in mind that bonnie++ isn't always going to reflect your real
performance.
I have run tests on some workloads that were definantly I/O limited where
bonnie++ results that differed by a factor of 10x made no measurable
difference in the application performance, so I can easily believe in
cases where bonnie++ numbers would not change but application performance
could be drasticly different.
as always it can depend heavily on your workload. you really do need to
figure out how to get your hands on one for your own testing.
David Lang
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