Re: [libvirt] qemu and <transient/> disks

On Mon, Jul 23, 2012 at 10:28:57AM +0100, Daniel P. Berrange wrote: > I agree with the quoted text that libvirt should define a > directory to use for the transient disks under /var/lib/libvirt/images > perhaps, and just use 'qemu-img create' to create that, and the > unlink it once QEMU has started up, so we can auto-cleanup > on QEMU shutdown. One issue here is that 'qemu-img create' is slow. 0.4 seconds to create a qcow2 file backing another file (ie. per readonly disk, and programs like virt-df may open dozens of readonly disks). I looked at the strace output and it seems the slowness is just overhead from the machinery of qemu's coroutines, and not connected with writing the qcow2 file, which is presumably why the qemu snapshot=on option is not noticably slow.