KVM Guest I/O slowness
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.