From: Roman Mamedov <rm@romanrm.ru>
To: Liam Kurmos <quantum.leaf@gmail.com>
Cc: Roberto Spadim <roberto@spadim.com.br>,
Brad Campbell <lists2009@fnarfbargle.com>,
Drew <drew.kay@gmail.com>, NeilBrown <neilb@suse.de>,
linux-raid@vger.kernel.org
Subject: Re: mdadm raid1 read performance
Date: Thu, 5 May 2011 10:06:10 +0600 [thread overview]
Message-ID: <20110505100610.66c93e08@natsu> (raw)
In-Reply-To: <BANLkTikQTKPuY+Mg8h9ZOkJPoEQ-jGTeLg@mail.gmail.com>
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On Thu, 5 May 2011 00:08:59 +0100
Liam Kurmos <quantum.leaf@gmail.com> wrote:
> in my tests i read 1GB and throw away the data.
> dd if=/dev/md0 of=/dev/null bs=1M count=1000
If you have enough RAM for disk cache, on the second and further consecutive
invocations of this you will be reading mostly from the cache, giving you an
incorrect inflated result. So either don't forget to drop filesystem caches
between runs, or just test read performance with "hdparm -t /dev/mdX" instead.
--
With respect,
Roman
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next prev parent reply other threads:[~2011-05-05 4:06 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-04 0:07 mdadm raid1 read performance Liam Kurmos
2011-05-04 0:57 ` John Robinson
2011-05-06 20:44 ` Leslie Rhorer
2011-05-06 21:56 ` Keld Jørn Simonsen
2011-05-04 0:58 ` NeilBrown
2011-05-04 5:30 ` Drew
2011-05-04 6:31 ` Brad Campbell
2011-05-04 7:42 ` Roberto Spadim
2011-05-04 23:08 ` Liam Kurmos
2011-05-04 23:35 ` Roberto Spadim
2011-05-04 23:36 ` Brad Campbell
2011-05-04 23:45 ` NeilBrown
2011-05-04 23:57 ` Roberto Spadim
2011-05-05 0:14 ` Liam Kurmos
2011-05-05 0:20 ` Liam Kurmos
2011-05-05 0:25 ` Roberto Spadim
2011-05-05 0:40 ` Liam Kurmos
2011-05-05 7:26 ` David Brown
2011-05-05 10:41 ` Keld Jørn Simonsen
2011-05-05 11:38 ` David Brown
2011-05-06 4:14 ` CoolCold
2011-05-06 7:29 ` David Brown
2011-05-06 21:05 ` Leslie Rhorer
2011-05-07 10:37 ` David Brown
2011-05-07 10:58 ` Keld Jørn Simonsen
2011-05-05 0:24 ` Roberto Spadim
2011-05-05 11:10 ` Keld Jørn Simonsen
2011-05-06 21:20 ` Leslie Rhorer
2011-05-06 21:53 ` Keld Jørn Simonsen
2011-05-07 3:17 ` Leslie Rhorer
2011-05-05 4:06 ` Roman Mamedov [this message]
2011-05-05 8:06 ` Nikolay Kichukov
2011-05-05 8:39 ` Liam Kurmos
2011-05-05 8:49 ` Liam Kurmos
2011-05-05 9:30 ` NeilBrown
2011-05-04 7:48 ` David Brown
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