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Date: Mon, 12 Nov 2001 22:53:23 +0100
From: Lionel Bouton <Lionel.Bouton@free.fr>
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To: Steve Lord <lord@sgi.com>
Cc: "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>
Subject: Re: File System Performance
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>
>
>
>I tried an experiment which puzzled me somwhat:
>
>> mount /xfs
>> cd /xfs/lord/xfs-linux
>> time tar cf /dev/null linux
>>
>
>real    0m7.743s
>user    0m0.510s
>sys     0m1.380s
>
>>hdparm -t /dev/sda5
>>
>
>/dev/sda5:
> Timing buffered disk reads:  64 MB in  3.76 seconds = 17.02 MB/sec
>
>>du -sk linux
>>
>173028  linux
>
>The tar got ~21 Mbytes/sec.
>
Things I'll check :

0/ rerun this test !!!
1/ is there cache on the scsi controler ?
2/ xfs data cached at mount ? (I don't believe so)
3/ "hdparm -t" is on crack.
4/ du reports a disk usage way ahead of files' sizes total (don't know 
xfs enough to estimate this propability) and tar won't read the whole 
"du -sk" data.


2/ "time mount /xfs" could help (if mount + tar times are below 
expected, this case can be eliminated).
3/ ask hdparm's maintener.
4/ tar, check tar size.

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