From mboxrd@z Thu Jan  1 00:00:00 1970
From: Roman Mamedov <rm@romanrm.net>
Subject: Re: write performance of HW RAID VS MD RAID
Date: Thu, 11 Jun 2015 05:27:29 +0500
Message-ID: <20150611052729.258dddfa@natsu>
References: <CAF1ivSa644NVVd5R=2g8rvbZ-FK5cgXy_U1XJjYwMf+TJdftCw@mail.gmail.com>
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To: Ming Lin <mlin@kernel.org>
Cc: linux-raid@vger.kernel.org, Neil Brown <neilb@suse.de>
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On Wed, 10 Jun 2015 15:27:07 -0700
Ming Lin <mlin@kernel.org> wrote:

> Hi NeilBrown,
>=20
> As you may already see, I run a lot of tests with 10 HDDs for the patchset
> "simplify block layer based on immutable biovecs"
>=20
> Here is the summary.
> http://minggr.net/pub/20150608/fio_results/summary.log
>=20
> MD RAID6 read performance is OK.
> But write performance is much lower than HW RAID6.
>=20
> Is it a known issue?

Did you tune the stripe_cache_size for the array? Try 32768.
https://peterkieser.com/2009/11/29/raid-mdraid-stripe_cache_size-vs-write-t=
ransfer/

--=20
With respect,
Roman

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