On Fri, Nov 08, 2013 at 05:13:00PM -0700, Eric Blake wrote: > On 11/08/2013 01:56 PM, Ian Main wrote: > > > > In qemu there will soon be drive-backup and block-backup commands that > > allow you to create backups or point-in-time snapshots of VM images. > > The original feature that drove this was to allow 'image fleecing', > > which involves creating a light weight mechanism to take a point in time > > snapshot of the running VM and access that remotely. > > > > You can get a good idea of the API from this post: > > > > http://lists.gnu.org/archive/html/qemu-devel/2013-10/msg02266.html > > > > I would like to see this available via libvirt and wanted to start > > working on a suitable API. I'm curious if anyone has any input on how > > they would like to see this done? While I have done some work with and > > on libvirt I'm no expert on the design philosophy behind the APIs so > > some direction here before I get coding would be much appreciated. > > > >>From what I can tell a volume based API that creates 'backups' and does > > the NBD export call could work but I'd like to hear if that's > > reasonable. > > It seems to me that a new API virDomainBlockBackup(domain, disk, > destination, bandwidth, flags) is probably the right approach, as well > as enhancing the existing virDomainBlockJob* to report job status and/or > abort the job early. OK that sounds good. How would it look if you wanted to NBD export the disk? Would that require a special desitination uri of some sort, or? Also in order to do that we need to run several commands against qemu including building a temporary image to store the original blocks. Is there an example command which already uses temporary storage that I could look at? > For that matter, we need to overhaul the job support. Right now, > virDomainBlockJob* assumes you can only have one outstanding job at a > time, which interferes with the notion of running fleecing from two > points in time. Similarly, there can only be one virDomainGetJobInfo > active. What we really need is a notion of a job id, a way to query the > job id most recently created by any existing job-related API, and a way > to query job status based on id rather than only the most-recently > started job. OK I can look at this too. I need to focus on getting the qemu patches in and then I'll start tackling all this. Ian > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org > -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list