What kernel are you running.
If your running 2.6.x use the deadline scheduler or downgrade to
2.4.23aavm 2.6.[0-9] has major problems with the IO scheduler since the
process scheduler is very fast now.
DVP
----
Dathan Vance Pattishall http://www.friendster.com
> -----Original Message-----
> From: Kevin Burton [mailto:burton@stripped]
> Sent: Friday, May 06, 2005 1:58 PM
> To: mysql@stripped
> Subject: MySQL not using optimum disk throughput.
>
>
> We have a few of DBs which aren't using disk IO to optimum capacity.
>
> They're running at a load of 1.5 or so with a high workload
> of pending queries.
>
> When I do iostat I'm not noticing much IO :
>
> Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s
> wkB/s
> avgrq-sz avgqu-sz await svctm %util
> sda 0.00 13.73 128.43 252.94 1027.45 1695.10 513.73
> 847.55 7.14 90.13 285.00 2.53 96.57
>
> ....
>
> This is only seeing about 500k -> 1M per second throughput.
>
> When I run bonnie++ on these drives they're showing 20M->40M
> throughput.
>
> Which is really strange.
>
> Most of our queries are single INSERTS/DELETES. I could
> probably rewrite these to become batch operations but I think
> I'd still end up seeing the above iostat results but with
> higher throughput.
>
> .... so I'd like to get to the bottom of this before moving forward?
>
> I ran OPTIMIZE TABLE on all tables but nothing.
>
> The boxes aren't paging.
>
> They're running on a RAID5 disk on XFS.
>
> Could it be that the disks are having to do a number of HEAD
> seeks since we have large tables?
>
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