From: Roman Mamedov <roman@rm.pp.ru>
To: Mikael Abrahamsson <swmike@swm.pp.se>
Cc: Shaochun Wang <scwang@ios.ac.cn>,
"linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>
Subject: Re: Write-intent bitmap decreases or increase performance of RAID5?
Date: Wed, 30 Jun 2010 14:23:28 +0600 [thread overview]
Message-ID: <20100630142328.6451f910@natsu> (raw)
In-Reply-To: <alpine.DEB.1.10.1006300857300.8623@uplift.swm.pp.se>
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On Wed, 30 Jun 2010 08:58:28 +0200 (CEST)
Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> On Wed, 30 Jun 2010, Roman Mamedov wrote:
>
> > This is not necessary. See the dd man page about the conv=fdatasync switch.
> > You can even test with just 256 MB this way, and still get an extremely
> > accurate result.
>
> You're right, for writing this is ok. For read tests it's important to use
> more than ram though, to avoid doing performance testing from block cache
> instead of from the actual drives.
Yeah, though there's also an alternative way of mitigating the effect of
the cache when testing read speed, see http://linux-mm.org/Drop_Caches
--
With respect,
Roman
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next prev parent reply other threads:[~2010-06-30 8:23 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-29 20:11 Write-intent bitmap decreases or increase performance of RAID5? Shaochun Wang
2010-06-30 5:18 ` Roman Mamedov
2010-06-30 5:54 ` Mikael Abrahamsson
2010-06-30 5:59 ` Roman Mamedov
2010-06-30 6:58 ` Mikael Abrahamsson
2010-06-30 8:23 ` Roman Mamedov [this message]
2010-06-30 18:31 ` CoolCold
2010-07-05 0:11 ` Bill Davidsen
2010-07-01 6:40 ` Shaochun Wang
2010-07-01 20:30 ` Majed B.
2010-07-01 20:50 ` Roman Mamedov
2010-07-05 0:14 ` Bill Davidsen
2010-07-01 20:49 ` Roman Mamedov
2010-07-02 11:13 ` John Robinson
2010-07-05 0:17 ` Bill Davidsen
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