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Re: Performance Characteristics of All Linux RAIDs (mdadm/bonnie++)

To: Jens Bäckman <jens.backman@xxxxxxxxx>
Subject: Re: Performance Characteristics of All Linux RAIDs (mdadm/bonnie++)
From: Chris Snook <csnook@xxxxxxxxxx>
Date: Wed, 28 May 2008 12:40:00 -0400
Cc: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, linux-raid@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <95711f160805280934y77ed7d91tec5aeb531bf8013c@mail.gmail.com>
References: <alpine.DEB.1.10.0805280442330.4527@p34.internal.lan> <95711f160805280934y77ed7d91tec5aeb531bf8013c@mail.gmail.com>
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Jens Bäckman wrote:
On Wed, May 28, 2008 at 10:53 AM, Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> wrote:
Results:

http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.html
http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.txt

Either the RAID 1 read speed must be wrong, or something is odd in the Linux implementation. There's six drives that can be used for reading at the same time, as they contain the very same data. 63MB/s sequential looks like what you would get from a single drive.

The test is a single thread reading one block at a time, so this is not surprising. If you get this doing multi-megabyte readahead, or with several threads, something is very wrong.


-- Chris


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