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?
> >
> 
>    Thanks for declaration, one more question:
> 3) will have a big image file, will you back up it or just leave it there, not
> backup for internal snapshot?

Sorry, I do not understand that question. Why will I have a 'a big image file', 
and
what do you mean by 'backup' exactly?