Re: [libvirt-users] Create qcow2 v3 volumes via libvirt
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
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