On Wed, Jun 29, 2011 at 12:59 PM, Kevin Wolf <kw...@redhat.com> wrote: > I'm not entirely sure if I should suggest writeback or none as the new > default, but I think it could make sense to change it.
I agree that cache=none is safe and fast with correct guests and local disks. It is beaten by cache=writeback in cases where the host has a lot of buffer cache to play with and the guest has very little - for example when running qemu without a -m argument. If I was running qemu-system-arm I might like cache=writeback. If I was virtualizing x86 servers I might like cache=none. cache=none as a default - which some management tools inherit - would be reasonable. Folks using command-line qemu can always tweak to use cache=writeback or even cache=unsafe if performance matters but data integrity does not. Whether it is safe to transition to cache=none or not depends on what broken guests are still widely deployed. Does CentOS 5 flush the disk cache? Stefan