Re: Again on IOPS higher than expected in randwrite 4k
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On 01/03/2011 12:05 PM, Jens Axboe wrote:
On 2011-01-02 05:12, Spelic wrote:Hello, I just subscribed, I noticed that some 20 days ago there was a thread on "IOPS higher than expected on randwrite, direct=1 tests" on this ML. It's curious because I subscribed to report basically the same thing. With Hitachi 7k1000 HDS721010KLA330 (maybe the same drives as Sebastian) I am seeing the same problem of IOPS too high with FIO, up to 300 IOPS per disk (up to 500 per disk with storsave=performance on my 3ware but that's probably cheating). I am doing 4k random writes. I followed the discussion, I don't really agree with the point at the end of the discussion, so I'd like to bump this thread again. My impression is that these drives do not honor the flush or FUA. (Directio uses flush or FUA right? you can be sure that data is on the platters after directio right? Anyway I also set fsync=1 and nothing changed)O_DIRECT does not imply flush of FUA, I'm afraid. It arguably should use FUA, but currently it does not.
Oh I see.But if I add fsync=1 I still get 300 IOPS per disk, or even 500 on very short seeks, so again I'd say these disks are cheating.
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