On Wed, 29 Jun 2011, Tom De Mulder wrote:
I have a set of 4 Intel 510 SSDs purely for testing, and I have used
these to simulate the kinds of workload I would expect them to
experience in a server environment (focused mainly on database access).
So far, those tests have focused on using single drives (ie. without
RAID) on a variety of controllers.
From the tests I have read, the Intel 510 are actually worse than the
Intel X-25 G1/G2/320 models, with exactly the symptoms you're describing.
It's fast for linear reads and writes, but not so good for random writes,
especially not when it's getting full.
Once the drives get fuller (something which does happen on servers) I do
indeed see write latencies that are in the order of several seconds (I
saw from 1500µs to 6000µs), as the drive suddenly struggles to free
entire blocks, where initially latency was in the single digits.
Yeah, this is a common problem especially for older drives. A lot has
happened with garbage collect but the fact is still that a lot of SSD
vendors have too little spare area, so the recommendation you make
regarding leaving a large area unused is something I do as well, and it
works.
I am hoping to get my hands on some Sandforce controller-based SSDs as well,
to compare, but even they show degradation as they get fuller in AnandTech's
tests (and those tests seem, IME, trustworthy).
Include the Intel 320 as well, I think it should be viable for your usage
pattern.
--
Mikael Abrahamsson email: swmike@xxxxxxxxx
