I have been using internal snapshots on
production qcow2 images for a couple of years, admittedly as
infrequently as possible with one exception and that exception has
had multiple snapshots taken and removed using virt-manager's GUI.
I was unaware of this:
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,
This might explain why this VM recently kept going into a paused
state and I had to extend the volume to get it to stay up. This
VM is used for testing our software in SharePoint and we make
heavy use of snapshots. Is there nothing I can to do recover that
space?
What would be the best practice then for a VM that needs to be
able to create and remove snapshots on a regular basis?
Paul O'Rorke
Tracker Software Products (Canada) Limited
www.tracker-software.com
Tel:
+1 (250) 324 1621
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On 2018-05-01 01:11 PM, Gionatan Danti
wrote:
Il
01-05-2018 10:56 Daniel P. Berrangé ha scritto:
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.
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 :-(
So internal snapshots remain something very useful for lab/tests,
but are not recommended for regular use in production environment,
right?
Thanks.
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