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 11:59:27 +0600 [thread overview]
Message-ID: <20100630115927.090751dd@natsu> (raw)
In-Reply-To: <alpine.DEB.1.10.1006300729150.8623@uplift.swm.pp.se>
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On Wed, 30 Jun 2010 07:54:55 +0200 (CEST)
Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> On Wed, 30 Jun 2010, Roman Mamedov wrote:
>
> > dd if=/dev/zero of=zerofile bs=1M count=2048 conv=fdatasync,notrunc
>
> To be a bit more sure about accurate measurement, make sure the amount of
> data you're transferring is twice the amount of RAM in the machine, the
> above is only 2 gigs of data.
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.
Three consecutive runs with "count=256" on a machine with 4GB of RAM:
268435456 bytes (268 MB) copied, 4.76846 s, 56.3 MB/s
268435456 bytes (268 MB) copied, 4.79682 s, 56.0 MB/s
268435456 bytes (268 MB) copied, 4.79307 s, 56.0 MB/s
--
With respect,
Roman
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next prev parent reply other threads:[~2010-06-30 5:59 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 [this message]
2010-06-30 6:58 ` Mikael Abrahamsson
2010-06-30 8:23 ` Roman Mamedov
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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