Interestingly, I had some VMs that were performing poorly on things that looked IO related – file copy, compiles etc. But I noticed today that the out of memory killer was hitting a few processes. These are server VMs, so no Xorg on them, so in theory they need little memory. I’d set them to respectively 256M and 384M (the second running mysql). I gave them 4GB of swap and thought I’d be fine.
They weren’t really using swap, and the OOM killer hit a few tasks. Given that I’m not really memory limited on the host (6GB), I figured I could afford to allocate more. Pushed both up to 512M and they run enormously differently. So maybe RAID performance isn’t all of my issue here. Might put in a birthday present request for more RAM….it’s an old Q6600, so the RAM isn’t too expensive for it.