Messages in this thread | | | From | Jeff Moyer <> | Subject | Re: [patch] Revert "block: remove artifical max_hw_sectors cap" | Date | Mon, 10 Aug 2015 13:23:48 -0400 |
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Christoph Hellwig <hch@infradead.org> writes:
> Hi Jeff, > > thanks for the detailed numbers! > > The bigger I/O size makes a drastic impact for Linux software RAID > setups, for which this was a driver. For the RAID5/6 over SATA disks > setups that I was benchmarking this it gives between 20 and 40% better > sequential read and write numbers.
Hi, Christoph,
Unfortunately, I'm unable to reproduce your results (though my test setup uses SAS disks, not SATA). I tried with a 10 data disk md RAID5, with 32k and 128k chunk sizes. I modified the fio program to read/write multiples of the stripe width, and I also used aio-stress over a range of queue depth and I/O sizes for read, write, random read and random write. I didn't see any measurable performance difference. Do you still have access to your test setup?
What do you think about reinstituting the artificial max_sectors_kb cap, but bumping the default up from 512KB to 1280KB? I had our performance team run numbers on their test setup (which is a 12 disk raid0 with 32k chunk size, fwiw) with max_sectors_kb set to 1280 and, aside from one odd data point, things looked good.
Cheers, Jeff
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