On Mon, Apr 30, 2018 at 08:42:56PM +0200, Gionatan Danti wrote:
Another question: how reliable are qcow2 ver2/3 files nowadays? Are you using them in production environments?
qcow2 is widely used in production at large scale in general. Just not with internal snapshots - almost everything uses external snapshots, aka backing file chains.
At the moment, I am using RAW files and filesystem-level snapshot to manage versioning; however, as virt-manager has direct support for managing qcow2 internal snapshots, it would be easier to deploy qcow2 disks.
What strikes me is that, if thing have not changed, Red Hat support policy was to *not* support internal snapshots. So, are they reliable enough for production VMs?
The QEMU community still tends to discourage use of internal snapshots. There are not even any QMP monitor commands to use them - you are forced to use the legacy HMP interface to QEMU for mgmt. All of the workaround providing interesting block storage mgmt is focused on external snapshots (aka the backing_file option). There are some technical downsides to internal snapshots IIUC, such as inability to free the space used by the internal snapshot when it is deleted, loading/saving snapshots blocks execution of the guest OS, and probably more I've forgotten about. The only nice thing about internal snapshots is simplicity of mgmt, and that is a very nice thing indeed, which is why virt-manager has code to support that - it was much easier to add that code for external snapshots. Just a shame about all the downsides :-( Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|