On Wed, Nov 07, 2018 at 13:22:32 +0800, Boxiang Zhu wrote:

Thanks for your reply. The nova project uses the virDomainBlockRebase API to finish the rebase operation from the old disk to the new disk not using the virDomainBlockCopy API.
I am confused of the difference of virDomainBlockRebase and virDomainBlockCopy.

virDomainBlockRebase way to do things was introduced to add the
functionality without having to add new API. Later we've figured out
that the new API is necessary anyways.

If you want to copy to a network location you'll need to use
virDomainBlockCopy. The old API does not support passing the disk
specification for non-local disks.

Note that as I've stated previously, the qemu driver does not allow
network disks with the new API until I finish integration with qemu's
'blockdev' feature which I'm currently working on.