On 06/04/2016 17:55, Alberto Garcia wrote: >> > [BB] overlay >> > | >> > | >> > [BDS] qcow2 [BB] backing >> > | | >> > +--------------------+ >> > . | >> > . I/O throttling >> > . | >> > [BDS] raw >> > . >> > . >> > . > I see, thanks for the explanation! > > But what's the use of having a BlockBackend on a node that is used as a > backing image? Is it because "we allow this so let's prevent the user > from doing weird things", or is there anything useful we can do with it?
The backing image can be the one that is visible to the guest, while the overlay can be a block-backup target (with 'sync':'none) whose BlockBackend is created by the NBD server. Paolo
