On Mon, Aug 22, 2011 at 04:01:08PM -0500, Anthony Liguori wrote: > On 08/22/2011 03:48 PM, Ryan Harper wrote: > >* Stefan Hajnoczi<stefa...@gmail.com> [2011-08-22 15:32]: > >>We wouldn't rm -rf block/* because we still need qemu-nbd. It > >>probably makes sense to keep what we have today. I'm talking more > >>about a shift from writing our own image format to integrating > >>existing storage support. > > > >I think this is a key point. While I do like the idea of keeping QEMU > >focused on single VM, I think we don't help ourselves by not consuming > >the hypervisor platform services and integrating/exploiting those > >features to make using QEMU easier. > > Let's avoid the h-word here as it's not terribly relevant to the discussion. > > Configuring block devices is fundamentally a privileged operation. > QEMU fundamentally is designed to be useful as an unprivileged user. > > That's the trouble with something like LVM. Only root can create > LVM snapshots and it's an all-or-nothing security model. > > If you want to get QEMU out of the snapshot business, you need a > file system that's widely available that allows non-privileged users > to take snapshots of individual files.
I don't think we should remove qcow2 internal snapshots or blockdev_snapshot. But they have performance limitations where it makes sense to start using existing storage support instead of reimplementing efficient and scalable snapshots ourselves. btrfs is maturing and its BTRFS_IOC_CLONE ioctl is unprivileged. So we can offer that option for unprivileged users. Stefan
