Re: [Qemu-devel] [RFC] qemu snapshot enchancement

[Dietmar Maurer]

> >>     My understanding is internal snapshots is obvious fast in both
> >> deleting and reading, and I have similar questions, Dietmar, could u
> >> tip more how you use this case while 2 snapshot layer exist?
> >
> > To be honest, I don't really understand what you talk about here.
> > There are simply different storage types and file formats. There are
> > several storage types with support for internal snapshots:
> >
> > * traditional qcow2 files on normal file system
> > * newer file systems (zfs, btrfs)
> > * lvm (new dm-thin pools)
> > * RDB (ceph)
> > * sheepdog
> > * iSCSI and nexenta API
> > *...
> >
> > And you simply want to allow an external library to create/remove the
> snapshot for you.
> >
> >
> >
>    I remember you have a patch enable take qcow2 internal snapshot for
> every block device, and then will you use LVM to take another LVM snapshot
> for it? If not how did you treat this qcow2 internal snapshot later?

No. Our VMs can have multiple disks on different storages. So we either use
qmp commands to create internal snapshots (qcow2), or external tools - that
depends on storage type.

Basically we do:

1.) save state
2.) pause VM
3.) use qmp commands to create internal snapshots for all disks which supports 
that
4.) use external tools to create snapshots for other disks (nexenta, btrfs, ...)
5.) resume the VM

Is that more clear now?