From what i know in the Citrix XEN implementation, they provide a way to read

hi, after watching Johns slides from the kvm forum (thanks for that) i had some quick look at the backup-v3 branch. Just to provide some feebdack for you guys, and some questions. My main question is about the part of the NBD backup. By default what you get from reading all the NDB data is a thick provisioned image of the domains disk. One can use the `qemu-img map' function to get a detailed information about the used blocks in the image, in case one wants to create a thin provisioned backup. As a third party backup vendor you cannot allways depend on qemu tools, because you might not even install any software on the host you are taking a backup from. So is, or will there be any way to get an output that represents the same information from the map function in the backup XML description via the libvirt API? Would it make sense to provide this information in the `backup-dumpxml' output? this information via the API, because they do not want the backup vendor to install any component on the host systems. Another thing i came across is that libvirt currently seems to forget about the running backup job if a domain is destroyed and started after a backup job was created: [root@x ~]# virsh backup-begin centos backup-pull.xml Backup id 1 started backup used description from 'backup-pull.xml' [root@x ~]# virsh destroy centos && virsh start centos [root@x ~]# virsh backup-end --id 1 centos error: Requested operation is not valid: No active block job 'tmp-hda' [root@x ~]# virsh backup-dumpxml --id 1 centos <domainbackup mode='pull' id='1'> <server transport='tcp' name='localhost' port='10809'/> <disks> <disk name='hda' type='file'> <driver type='qcow2'/> <scratch file='/vm/base.img.1542876138'/> </disk> </disks> </domainbackup> thanks for your hard work on this! bye, - michael