What version did Live Snapshots get introduced in?

[Scott Baker]

What version do I need to support live snapshots? I'm seeing:

virsh snapshot-create-as Test123 snapshot1 "before yum upgrade"
--disk-only --atomic

Compiled against library: libvirt 0.10.2
Using library: libvirt 0.10.2
Using API: QEMU 0.10.2
Running hypervisor: QEMU 0.12.1

[Cole Robinson]

On 10/09/2013 04:52 PM, Scott Baker wrote:
> What version do I need to support live snapshots? I'm seeing:
>
> virsh snapshot-create-as Test123 snapshot1 "before yum upgrade"
> --disk-only --atomic

What happens if you run that command? If virsh supports those options and
doesn't throw an error, then your versions are new enough :)

Though if you don't know, using disk only snapshots as to try something and
then rollback or merge is not trivial, since snapshot-revert and
snapshot-delete are not wired up so you have to do it all by hand.
> Compiled against library: libvirt 0.10.2
> Using library: libvirt 0.10.2
> Using API: QEMU 0.10.2
> Running hypervisor: QEMU 0.12.1

Are you using RHEL/CentOS? Not sure what versions there, but for Fedora you
need Fedora18 and later.

- Cole

[Andrew Cathrow]

----- Original Message -----
> From: "Cole Robinson" 
> To: "Scott Baker" , "Fedora Virt" 
> Sent: Thursday, October 10, 2013 9:49:53 AM
> Subject: Re: [fedora-virt] What version did Live Snapshots get introduced in?
>
> On 10/09/2013 04:52 PM, Scott Baker wrote:
> > What version do I need to support live snapshots? I'm seeing:
> >
> > virsh snapshot-create-as Test123 snapshot1 "before yum upgrade"
> > --disk-only --atomic
>
> What happens if you run that command? If virsh supports those options and
> doesn't throw an error, then your versions are new enough :)
>
> Though if you don't know, using disk only snapshots as to try something and
> then rollback or merge is not trivial, since snapshot-revert and
> snapshot-delete are not wired up so you have to do it all by hand.
> > Compiled against library: libvirt 0.10.2
> > Using library: libvirt 0.10.2
> > Using API: QEMU 0.10.2
> > Running hypervisor: QEMU 0.12.1
>
> Are you using RHEL/CentOS? Not sure what versions there, but for Fedora you
> need Fedora18 and later.

Judging by the version of QEMU it sounds like it's RHEL/CentOS.
There qemu version in RHEL 6.x doesn't include live snapshots, that was added well after 0.12 and wasn't backported.
If you're running RHOS or RHEV on top of RHEL 6 they come with a different version of qemu that has more features including livesnapshot and storage migration.
I'm not sure if those packages are rebuilt by CentOS.
> Cole
>
> virt mailing list
> [e-mail]
> https://admin.fedoraproject.org/mailman/listinfo/virt

[Eric Blake]

On 10/09/2013 02:52 PM, Scott Baker wrote:
> What version do I need to support live snapshots? I'm seeing:
>
> virsh snapshot-create-as Test123 snapshot1 "before yum upgrade"
> --disk-only --atomic

Non-live internal snapshots have been around for a long time (qemu 0.11?
and somewhere in the libvirt 0.8.x timeframe) - but that requires not
using the --disk-only option.

Live internal snapshots are a future possibility (it looks like qemu 1.7
will be adding 'blockdev-snapshot-internal-sync') - but libvirt will
have to be taught to use it, so that won't be any sooner than libvirt
1.1.4, and more likely several months out.

External snapshots (ie. using --disk-only) have always been live; and
requires 'blockdev-snapshot-sync', introduced in qemu 0.14; --atomic
requires 'transaction', introduced in qemu 1.1.  External snapshots in
libvirt require libvirt 0.9.5 for disk-only, or libvirt 1.0.5 for memory
alongside the disk snapshot.

Of course, various distros have backported some of these features onto
builds that report earlier version numbers, so sometimes you just have
to try it and see if it has been backported.