Hi, With the current changes of block copy implementation in qemu (which was dropped in favor of using image streaming and snapshots to do the job) I think it's best not to include virDomainBlockCopy API in libvirt (yet). This is for several reasons: - the ideal semantics of virDomainBlockCopy API would be a no-op in case of failure, which can't be achieved with snapshot/image streaming combo since the domain is switched to the new image before any copying starts instead of when everything is finished - since monitor/cancellation APIs are designed with future block operations in mind, it will be easy to provide virDomainBlockCopy in the future if we feel the need for it - with BlockPull and Snapshot APIs in place, users/apps can do block copy by creating a snapshot of a disk and running BlockPull on it to make the new image independent on the original disk image - the two phase process makes it easy to resume image streaming in case it failed for a recoverable reason With current (WIP) snapshot support, one would use virDomainSnapshotCreateXML asking for a disk snapshot only (no memory) with the following XML: <domainsnapshot> <name>whatever</name> <disk name='/path/to/image1' snapshot='no'/> <disk name='/path/to/image2' snapshot='yes'> <volsnapshot> <name>disk snapshot name</name> <image name='/another/path/to/image2.new'/> </volsnapshot> </disk> </domainsnapshot> This will switch the domain to /another/path/to/image2.new with /path/to/image2 as its backing store. The new image can then be made independent on its backing store by calling virDomainBlockPull on it. Jirka