On Wed, Oct 16, 2013 at 03:15:30PM -0600, Chris Murphy wrote: > > On Oct 16, 2013, at 1:09 PM, Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote: > > > > > > I made the suggested cache change for both LVM and qcow2; and created the qcow2 file as suggested (adding lazy_refcount): > > > > Fedora 20 default standard partition guided install (ext4) to an LV takes 18m02s. Firstboot systemd-analyze: > > Reboot, first boot systemd-analyze results: 852ms (kernel) + 1.425s (initrd) + 10.417s (userspace) = 12.695s > > > > The same install parameters to qcow2 on XFS takes 17m52s. Firstboot systemd-analyze: > > 829ms (kernel) + 1.475s (initrd) + 11.693s (userspace) = 13.998s > > Same unsafe caching and qcow2 '-o preallocation=metadata,compat=1.1,lazy_refcounts=on' as above > > Fedora 20 default BTRFS guided install to qcow2 on XFS, install time 17m21s. Firstboot systemd-analyze: > 874ms (kernel) + 1.558s (initrd) + 12.866s (userspace) = 15.300s > > The install is a tiny bit faster than the ext4 standard partitions > (no LVM) result above, only difference is ext4 vs btrfs. > > But it's a ton faster than the originally reported btrfs to qcow2 on > XFS result of 1h11m. Clearly it wasn't the file system that slowed > it down. FWIW this is still /boot on ext4 not on btrfs, so kernel > and initrd results are ext4 and userspace is primarily btrfs. > > It'd be great if virt-manager defaults to using these qcow2 options, > short of them causing some sort of problem. I can't tell from the > qemu-img info command what options were used to create the file. ^ Cole: Chris reports (and it matches my experience) that using the qemu-img / qcow2 options preallocation=metadata,compat=1.1,lazy_refcounts=on greatly improves write performance of qcow2 disks. This of course requires qemu >= 1.1 (and >= 1.5 for lazy_refcounts). Is this something which virt-manager should use? I don't see it in the current code, but libvirt supports at least preallocation=metadata & lazy_refcounts. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming blog: http://rwmj.wordpress.com Fedora now supports 80 OCaml packages (the OPEN alternative to F#) -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
