March 7th, 2012

Brace yourselves.Winter is coming back

Dear Diary,

I’ve now found some time to do further speed testing of the SSD machine that’s going to replace the Gmane news server.  I know that you remember everything, Diary, but let me give you a brief recap.

I got a bunch of 512GB Samsung 830 SATA3 SSDs that are supposed to have IOPSes coming out of their ears. I got a RAID card, hooked it up, and was somewhat underwhelmed by the performance.  I got a read performance of 4400 files per second when reading in kinda-random order, despite the RAID card having SATA3 and a special “key” that was supposed to disable the built-in slowdowns. That’s ok, but not extremely impressive.

So today I hooked the SSDs up the the motherboard directly.  Unfortunately the motherboard only has SATA2, so the theoretical single-disk bandwidth is about 270MB/s.  Pitiful.

And, wouldn’t you know it, large-file performance towards a single disk was 250MB/s when writing, and 265MB/s when reading. For small files, I get 4000 files per seconds, and 32MB/s.

So pretty much as expected.

Then I created a soft RAID5 over the disks.  Large-file performance is 520MB/s, which is less than half of what I got on the SATA3 RAID card.  The small file performance is 4200 files per second, which is just vaguely south of what that supposedly spiffy RAID card gave me.

This is all rather disappointing.

Diary, I’ll try once more with the RAID card, mixing up the RAID parameters, but I have little hope that much will change.  I’ll have to settle for 4K/s performance when serving out messages from news.gmane.org, I think.

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