Re: RAID 0 not as fast as expected

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From: Luke Lonergan <llonergan@greenplum.com>
To: Joshua Drake <jd@commandprompt.com>
Cc: Craig A. James <cjames@modgraph-usa.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: RAID 0 not as fast as expected
Date: Thu, 14 Sep 2006 20:51:42 -0700
Message-ID: <C12F715E.3112D%llonergan@greenplum.com> (raw)
In-Reply-To: <450A226B.6050405@commandprompt.com>

Josh,

On 9/14/06 8:47 PM, "Joshua D. Drake" <jd@commandprompt.com> wrote:

>> I've obtained 1,950 MB/s using Linux software RAID on SATA drives.
> 
> With what? :)

Sun X4500 (aka Thumper) running stock RedHat 4.3 (actually CentOS 4.3) with
XFS and the linux md driver without lvm.  Here is a summary of the results:

     
 Read Test      
 RAID Level Max Readahead (KB) RAID Chunksize Max Readahead on Disks (KB)
Max Time (s)  Read Bandwidth (MB/s)
 0 65536 64 256 16.689  1,917.43
 0 4096 64 256 21.269  1,504.54
 0 65536 256 256 17.967  1,781.04
 0 2816 256 256 18.835  1,698.96
 0 65536 1024 256 18.538  1,726.18
 0 65536 64 512 18.295  1,749.11
 0 65536 64 256 18.931  1,690.35
 0 65536 64 256 18.873  1,695.54
 0 64768 64 256 18.545  1,725.53
 0 131172 64 256 18.548  1,725.25
 0 131172 64 65536 19.046  1,680.14
 0 131172 64 524288 18.125  1,765.52
 0 131172 64 1048576 18.701  1,711.14
 5 2560 64 256 39.933  801.34
 5 16777216 64 256 37.76  847.46
 5 524288 64 256 53.497  598.16
 5 65536 32 256 38.472  831.77
 5 65536 32 256 38.004  842.02
 5 65536 32 256 37.884  844.68
 5 2560 16 256 41.39  773.13
 5 65536 16 256 48.902  654.37
 10 65536 64 256 83.256  384.36
 1+0 65536 64 256 19.394  1,649.99
 1+0 65536 64 256 19.047  1,680.05
 1+0 65536 64 256 19.195  1,667.10
 1+0 65536 64 256 18.806  1,701.58
 1+0 65536 64 256 18.848  1,697.79
 1+0 65536 64 256 18.371  1,741.88
 1+0 65536 64 256 21.446  1,492.12
 1+0 65536 64 256 20.254  1,579.93

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