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Date:      Mon, 21 Aug 2006 18:42:34 +0200
From:      "Chris Knipe" <savage@savage.za.org>
To:        "Dan Nelson" <dnelson@allantgroup.com>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: sluggish disk performance.
Message-ID:  <003701c6c540$d0744f20$0a01a8c0@superman>
References:  <000701c6c539$bbb33710$0a01a8c0@superman> <20060821162156.GB45306@dan.emsphone.com>

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> In the last episode (Aug 21), Chris Knipe said:
>> Disks   ad0                               ofod            intrn
>> KB/t  16.83                               %slo-z    35456 buf
>> tps     103                             4 tfree       414 dirtybuf
>> MB/s   1.70                                         20988 desiredvnodes
>> % busy   98                                          5247 numvnodes
>>                                                     4223 freevnodes
>> 
>> Got 1 ATA100 Seagate 120GB disk in there at the moment.... 1.7MB/s at
>> 98% busy?  Surely, that figure is WAY low???  I'd expect atleast
>> about 10MB/s on ATA100.
> 
> That number's about right for random I/O and small blocksizes, which is
> what the KB/t field shows.  If you were doing sequential I/O, the KB/t
> field would be at or near 128.  Are you also running a "du", "cvs
> update", or other command likely to be doing random disk accesses?

ALTER TABLE on a 200MB mySQL table?  

I guess its time for a dedicated disk then.... 

--
C




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