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Re: [libvirt] RFC backup API

On 03/21/2016 04:18 AM, Maxim Nestratov wrote:
> Hi all,
> It's been already quite a long time since qemu implemented QMP
> "drive-backup" command to create block devices backups. Even more, since
> qemu 2.4 there is a possibility to create incremental backups. Though it
> is possible to backup all attached to a domain disk drives by combining
> them into a single QMP transaction command, this way of creating them,
> not to mention managing, remains inconvenient for an end user of
> libvirt. Moreover, creating a single drive backup via QMP interface
> isn't handy either. That said, it looks reasonable to introduce a *new
> backup API* based on QMP "drive-backup" facilities.
> Though we can start from a single simple function, allowing to create a
> disk backup by means of QMP "drive-backup" command, I'd like to discuss
> here the level of management libvirt could provide for backup
> operations. To begin with, here is the preliminary list of possible
> functions that I think make sense for libvirt API.
> virDomainCreateBackup - which creates a backup full/incremental of
> all/selected disks,

I'm also wondering if it would be better to just add a new flag to our
existing virDomainBlockCopy() that specifies backup semantics (the
current default creates the block copy at the point in time that the job
is _ended_; whereas drive-backup creates the block copy at the oin in
time where the job is _started_), rather than needing new API.

> virListBackups - which lists all backups created for a particular
> domain/target,
> virRestoreBackup - which restores all/selected disks from a backup,
> virDeleteBackup - which deletes all/selected disks from a backup.

And here, I think that the existing virDomainSnapshot* API may already
fit this need, if we could more closely couple the act of creating
snapshots/backups with the act of disk backups.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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