sluggish disk performance.

Chris Knipe savage at savage.za.org
Mon Aug 21 16:42:54 UTC 2006


> 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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