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klocika 25th January 2013 23:00

KVM Guest I/O slowness
Hi all,

I have a KVM cluster running on CentOS 6.3. All the guests are CentOS 6.3 also. All hosts are connected to a SAN, the base filesystem is gfs2.

I cloned some mysql cluster nodes from each other, they are on the same LUN, but one of them can do approx. 200 000 IO/sec, the other ones can do only 2-4000 IO/sec.

My guests use LVM with cache='none' io='native' settings.

If you have any idea please help me. I think something went wrong with the blocks, but I really don't know, coz the LVMs are on the same LUN and the IO during clone is more then 500000/sec.


falko 28th January 2013 15:30

Have you tried cache='writethrough' and io='threads'?

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