Re: RAID 0 not as fast as expected

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From: Joshua D. Drake <jd@commandprompt.com>
To: Luke Lonergan <llonergan@greenplum.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 21:01:24 -0700
Message-ID: <450A2594.8080404@commandprompt.com> (raw)
In-Reply-To: <C12F715E.3112D%llonergan@greenplum.com>
References: <C12F715E.3112D%llonergan@greenplum.com>

Luke Lonergan wrote:
> 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:
> 


Good god!

>      
>  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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