Messages in this thread | | | From | Jeff Moyer <> | Subject | Re: [patch] Revert "block: remove artifical max_hw_sectors cap" | Date | Mon, 20 Jul 2015 16:44:26 -0400 |
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Jens Axboe <axboe@kernel.dk> writes:
> On 07/20/2015 01:17 PM, Jeff Moyer wrote: >> >> <resent with Jens' email address fixed> >> >> Hi, >> >> This reverts commit 34b48db66e08, which caused significant iozone >> performance regressions and uncovered a silent data corruption >> bug in at least one disk. >> >> For SAN storage, we've seen initial write and re-write performance drop >> 25-50% across all I/O sizes. On locally attached storage, we've seen >> regressions of 40% for all I/O types, but only for I/O sizes larger than >> 1MB. > > Do we have any understanding of where this regression is coming from? > Even just basic info like iostats from a run would be useful.
I'll request this information and get back to you. Sorry, I should have done more digging first, but this seemed somewhat urgent to me.
>> In addition to the performance issues, we've also seen data corruption >> on one disk/hba combination. See >> http://marc.info/?l=linux-ide&m=143680539400526&w=2 > > That's just sucky hardware... That said, it is indeed one of the > risks. We had basically the same transition from 255 as max sectors, > since we depended on ATA treating 0 == 256 sectors (as per spec).
Sure, the hardware sucks. I still don't like foisting silent data corruption on users. Besides, given that this patch went in without any performance numbers attached, I'd say the risk/reward ratio right now is in favor of the revert.
Cheers, Jeff
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