I wrote an experimental btrfs storage pool which uses subvolumes (and optionally snapshots) as storage volumes in LXC domains. The code is available at https://github.com/saaros/libvirt/compare/btrfs-storage but it's still missing some features like quotas for the subvolumes (currently the capacity definition for volumes is ignored) and doesn't have any documentation so far. Sample usage: mkdir /virtual; mkfs.btrfs /dev/vdb; mount -t btrfs /dev/vdb /virtual virsh pool-create-as testpool btrfs --target /virtual virsh vol-create-as testpool vanilla 0 echo vanilla > /virtual/vanilla/test virsh vol-create-as testpool test 0 --backing-vol vanilla cat /virtual/test/test btrfs subvolume list /virtual Does this look like a useful feature and does it make sense to implement it as a new storage pool type, or should it be merged into an existing one? I looked at the existing ones and couldn't really figure out how to make it fit nicely in any of them. As far as I could tell none of the existing storage pools or volumes offered a way to create a new copy-on-write volume for easy use in LXC domains using the libvirt API. With the new btrfs pool I was able to replace KVM domains using qcow2 volumes with LXC + btrfs with very little changes to the application code. Cheers, Oskari