linux-kernel - Re: [patch] Revert "block: remove artifical max_hw

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Message-ID: <x49k2thivql.fsf@segfault.boston.devel.redhat.com>
Date:	Thu, 30 Jul 2015 10:08:18 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	dmilburn@...hat.com
Subject: Re: [patch] Revert "block: remove artifical max_hw_sectors cap"

Christoph Hellwig <hch@...radead.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.

OK, thanks for the details on the setup.  Did you try with max_sector_kb
values between 512 and 32767?  I wonder if we can find a happy middle
ground, like 1280 or even 2048.

I'll try to setup a software raid 5 with 10 disks and get back to you.
If you have a preference for the exact geometry, please speak up.

Thanks!
Jeff
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