On Wed, May 02, 2018 at 02:45:05PM +0200, Gionatan Danti wrote:
> On 01/05/2018 22:49, Gionatan Danti wrote:
> > Ok, I think I'll continue to use RAW images + filesystem snapshots +
> > external snapshot when required.
> > It is unfortunate that we have no GUI to manage external snapshots. I
> > even remember that external snapshot remove was not supported - I had to
> > use the --metadata flag and a plain "rm" to remove them (or using
> > --no-metadata in the first place)[1]. Does it remain the current
> > behavior?
Yes, you still have to clean up external snapshot metadata manually, as
the link below indicates. Deleting external snapshots is a non-trivial
problem. For example, if you have a disk image chain like:
[A] <-- [B] <-- [C] <-- [D]
Now if you no longer need image [B], what is the most efficient way to
get rid of it? Three possibilities:
- Merge [B] into [A], and rewrite the backing chain of [C]
to point to [A]. Now can you discard image [B].
- Merge [A] into [B], call the new image [AB]. Now you can
discard [A].
- Merge [B] into [C], and rewrite the backing chain of [C] to point to
[A]. Now you can discard image [B].
It depends on how large each of the disk images are, and based on the
size, merge / coalesce them accordingly, to arrive at the quickest
solution.
Note that existing commands (`virsh blockpull` and `virsh blockcommit`,
which is relatively faster) will allow you handle it manually or script
it -- which many people already do it.
A couple of references (that are also easily scriptable):
http://wiki.libvirt.org/page/Live-merge-an-entire-disk-image-chain-including-current-active-disk
https://wiki.libvirt.org/page/Live-disk-backup-with-active-blockcommit
> > [1]
> > https://www.redhat.com/archives/libvirt-users/2015-September/msg00037.html
>
> Any hope to get virsh external snapshot creation/deletion fixed?
I don't see any problem creation external snapshots (or more correctly:
"overlays"). Deletion of external snapshots involves a bit more work,
but it is scriptable as well.
[...]
--
/kashyap
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