On Fri, Feb 05, 2016 at 11:28:42AM +0300, Denis V. Lunev wrote:
> On 02/03/2016 11:14 AM, Fam Zheng wrote:
> >On Sat, 01/30 13:56, Vladimir Sementsov-Ogievskiy wrote:
> >>Hi all.
> >>
> >>These series which aims to add external backup api. This is needed to allow
> >>backup software use our dirty bitmaps.
> >>
> >>Vmware and Parallels Cloud Server have this feature.
> >What is the advantage of this appraoch over "drive-backup sync=incremental
> >..."?
> 
> This will allow third-party vendors to backup QEMU VMs into
> their own formats or to the cloud etc.

As an example, there is a third-party backup format called VMA from
Proxmox.  A few years ago I posted a proof-of-concept external backup
tool in Python:

https://lists.gnu.org/archive/html/qemu-devel/2013-03/msg01536.html

It takes a full backup using drive-backup NBD (plus RAM/device state)
but the same can be done with incremental backups.

Does this NBD approach meet your requirements?

Stefan