From: Nikolay Kichukov <hijacker@oldum.net>
To: Roman Mamedov <rm@romanrm.ru>
Cc: Liam Kurmos <quantum.leaf@gmail.com>,
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, 05 May 2011 11:06:09 +0300 [thread overview]
Message-ID: <4DC25A71.6090705@oldum.net> (raw)
In-Reply-To: <20110505100610.66c93e08@natsu>
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Hi,
It seems like he is reading directly from the raid device and not through the filesystem. So there are no filesystem
caches in this way.
Cheers,
- -Nik
On 05/05/2011 07:06 AM, Roman Mamedov wrote:
> 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.
>
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next prev parent reply other threads:[~2011-05-05 8:06 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
2011-05-05 8:06 ` Nikolay Kichukov [this message]
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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