Vishvananda Ishaya wrote: > > On May 10, 2012, at 1:56 AM, Daniel P. Berrange wrote: > >> On Thu, May 10, 2012 at 09:06:58AM +0100, Daniel P. Berrange wrote: >> >> I had a quick chat with Kevin Wolf who's the upstream QEMU qcow2 >> maintainer >> and he said that 64k is the current recommended cluster size for qcow2. >> Above this size, the cost of COW becomes higher causing an overall >> drop in performance. >> >> Looking at GIT history, Nova has used cluster_size=2M since Vish first >> added qcow2 support, and there's no mention of why in the commit message. >> So unless further info comes to light, I'd say we ought to just switch >> to use qemu-img's default setting of 64K for both Xen and KVM. >> > > This is good info. Sounds like we should switch to 64K
Right. I'll submit a patch for that shortly. Regards, Jim _______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : openstack@lists.launchpad.net Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp