The thing I find strange about this is that our experience (@ Meetup) seems to match that of Friendsters (I know of a few other high traffic sites that have mentioned similar issues), in that Mysql on Opteron and Linux 2.6 is not a good solution. Yet, Mysql recommends exactly this config and in fact, does not seem to even support (via support contract) a 2.4 solution for Opteron + Mysql.
Greg
Dathan Pattishall wrote:
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:[EMAIL PROTECTED] Sent: Friday, May 06, 2005 1:58 PM
To: mysql@lists.mysql.com
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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