On 17 Feb 2009, at 6:39 pm, Ruslan Zakirov wrote: > I hope you see that mysql examined only 27 rows and spend 240 seconds > to do that. I suspect that it's related to very high IO activity that > were going parallel with this query and blocked mysql's IO requests.
That was my worry. I've shuffled the virtual machine onto a physical server with no other VM's running, and the performance problem remains the same. The graph of disk I/O from the VMware control center shows the system doing no I/O at all until I start the SELECT, and then it goes to about 15 MB/sec for the duration of the query. So if there is contention, it's not at the level of the physical server's I/O. However, it could still be contention for the SAN volume which hosts the virtual machine; I find this hard to believe since the total I/O of all three physical servers is pretty low, but I will try tomorrow to see what happens if I move the virtual machine to its own piece of storage, Tim -- The Wellcome Trust Sanger Institute is operated by Genome Research Limited, a charity registered in England with number 1021457 and a company registered in England with number 2742969, whose registered office is 215 Euston Road, London, NW1 2BE. _______________________________________________ http://lists.bestpractical.com/cgi-bin/mailman/listinfo/rt-users Community help: http://wiki.bestpractical.com Commercial support: [email protected] Discover RT's hidden secrets with RT Essentials from O'Reilly Media. Buy a copy at http://rtbook.bestpractical.com
