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

[Stefan Hajnoczi]

On Fri, Mar 8, 2013 at 6:44 PM, Dietmar Maurer <address@hidden> wrote:
>> >> 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?

Yes.  I sent an RFC series that shows this approach.  It is just a
prototype but it demonstrates that the NBD approach works and performs
reasonably well for a quick Python hack.

The stripped down patch series needs:
1. (Optional) query-block virtual_size field if management tool needs
to query drive size
2. Patch 2/6 with review comments addressed
3. 'block-backup' QMP command (and optionally HMP command)

That's it!

Stefan