From: Tomasz Chmielewski <mangoo@wpkg.org>
To: adfas asd <chimera_god@yahoo.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: Disappointing RAID10 Performance
Date: Fri, 16 Oct 2009 20:30:27 +0200 [thread overview]
Message-ID: <4AD8BBC3.4030600@wpkg.org> (raw)
In-Reply-To: <364346.70897.qm@web38808.mail.mud.yahoo.com>
adfas asd wrote:
> I was hoping to get better performance with RAID10 than from the raw disks, but that's turned out to not be the case. Experimenting with the readahead buffer I get these bandwidths with the following command:
> # time dd if={somelarge}.iso of=/dev/null bs={readahead size}
>
> /dev/sd?
> 1024 71.3 MB/s
> 2048 71.2 MB/s
> 4096 77.7 MB/s
> 8192 69.4 MB/s
> 16384 76.6 MB/s
>
> /dev/md2
> 1024 67.1
> 2048 69.1
> 4096 75.7
> 8192 64.9
> 16384 69.0
>
> Using RAID10offset2 on 2 WD 2TB drives, and always the same input file.
>
> Why would RAID10 performance be -poorer-?
If you only use your RAID-10 array for a single "dd if=bigfile
of=/dev/null" then yes, it does not give you much over mirroring.
If you start using your drives for two "dd if=bigfile[12] of=/dev/null"
at the same time, you will notice the difference.
--
Tomasz Chmielewski
http://wpkg.org
next prev parent reply other threads:[~2009-10-16 18:30 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-16 17:32 Disappointing RAID10 Performance adfas asd
2009-10-16 17:36 ` Majed B.
2009-10-16 18:10 ` Rob Becker
2009-10-16 21:05 ` adfas asd
2009-10-21 23:26 ` Bill Davidsen
2009-10-16 18:30 ` Tomasz Chmielewski [this message]
2009-10-17 16:12 ` Asdo
2009-10-17 16:20 ` Tomasz Chmielewski
2009-10-17 21:35 ` Majed B.
2009-10-18 11:01 ` Michael Tokarev
2009-10-16 21:20 ` Christopher Chen
2009-10-18 12:06 ` adfas asd
2009-10-16 21:27 ` Keld Jørn Simonsen
2009-10-17 6:03 ` Leslie Rhorer
2009-10-18 12:17 ` adfas asd
[not found] <7bc80d500910161433l49cbf599m80310082b6fdaa97@mail.gmail.com>
2009-10-18 12:14 ` adfas asd
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