Re: [Qemu-devel] [PATCH v4 3/6] add backup related monitor commands

[Dietmar Maurer]

> >> 1. QEMU can neither backup nor restore without help from the management
> >>    tool.
> >
> > Backup works perfectly with the current patches. You can easily
> > trigger a backup using a HMP command. This is not really important, but 
> > works.
> 
> If you send me a VMA file I can't restore it without knowing your command-line
> and possibly setting up the environment.  QEMU just can't do that, it's out of
> scope.  That is why the backup archive is a management tool concept.

I don't really know why you insist on that claim. I can do a backup with hmp 
command,
and then restore that later using the management tools. I just need to issue the
correct hmp backup command.

But this is not relevant for this discussion, so let us continue. We talked 
about the overhead
of the additional IPC layer.

> 
> >> This is a strong indicator that the backup archive code should
> >>    live outside QEMU.  I doesn't make sense for proxmox, oVirt,
> >>    OpenStack, and others to each maintain their backup archive code
> >>    inside qemu.git, tied to QEMU's C codebase, release cycle, and
> >>    license.
> >> 2. QEMU already has interfaces to export the vmstate and block device
> >>    snapshots: migration/savevm and BlockDriverState (NBD for IPC or
> >>    raw/qcow2/vmdk for file).  It is not necessary to add a
> >>    special-purpose interface just for backup.
> >>
> >> 3. The backup block job can be composed together with other QMP
> commands
> >>    to achieve scenarios besides just VMA backup.  It's more flexible to
> >>    add simple primitives that can be combined instead of adding a
> >>    monolithic backup command.
> >>
> >> For these reasons, I'm against putting backup archive code into QEMU.
> >
> > That is OK for me - I already maintain the code outside of qemu.
> 
> Does this mean you will keep this patch series out-of-tree?
> 
> What I am looking for is a stripped down patch series with just a backup block
> job (no backup archive writer or migration code).  That would be easily merged
> and saves you front rebasing this series as QEMU changes.

That is Patch 2/6?