Matthew Hawn <steamraven <at> yahoo.com> writes: > > What are the recommendations for running KVM images on BTRFS systems using kernel 3.4? I saw older > posts on the web complaining about poor performance, but I know a lot of work has gone into btrfs since then. > There also seemed to be the nocow option, but I didn't find anything that said it actualy helped. > Running KVM image files on btrfs as of yesterday. Used mkfs.btrfs -l 32k -n 32k to create and default options only (no mount options bar defaults, so no compression (just asking for trouble!), or autodefrag). 3.4.1 official Debian AMD64 kernel. Multi-subvol including root with set-default enacted. 32k's adopted per Chris's post. Install: virt-install --connect qemu:///system -n china -r 256 --disk path=/var/lib/libvirt/images/china.img,size=4 -c /home/alex/debian-testing-amd64-CD-1.iso --vnc --noautoconsole --os-type linux --os-variant debianwheezy --accelerate --network=bridge:br0 --hvm This runs much slower than expected - have done many debian bare minimum installs like this before. Can't hear any disk thrashing. Doesn't appear to be CPU or memory bound - will double check. Want to add autodefrag option but saw a comment about it on the wiki gotchas page or here (~ need to make sure it doesn't multi invoke or sommat?). In contrast, VirtualBox 60GB WindowsXP guests quite happy running and very quick on standard btrfs 3.3.7 kernel create in ArchLinux - with absolutely no flash stuff. Didn't create them in btrfs though (XFS). That may be the difference: level of churn in the file. Saw a post about using filefrag program on btrfs and want to try that. Questions? -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
