Il 18/03/2013 18:38, George Dunlap ha scritto: >>> >> This might be a difference between Xen and KVM. On Xen migration is >> made to a server in a paused state, and it's only unpaused when >> the migration to B is complete. There's a sort of extra handshake at >> the end. > > I think what you mean is that all the memory is handled by Xen and the > toolstack, not by qemu. The qemu state is sent as the very last thing, > after all of the memory, and therefore (you are arguing) that qemu is > not started, and the files cannot be opened, until after the migration > is nearly complete, and certainly until after the file is closed on the > sending side.
That would be quite dangerous. Files aren't closed until after QEMU exits; at this point whatever problem you have launching QEMU on the destination would be unrecoverable. Even for successful migration, it would also be bad for downtime (QEMU isn't exactly lightning-fast to start). And even if failure weren't catastrophic, it would be a pity to transfer a few gigs of memory and then find out that QEMU isn't present in the destination. :) Still, it's more than possible that I've forgotten something about Xen's management of QEMU. > (In KVM this isn't the case because I assume it's qemu that handles the > memory transition, and so it is likely to open the files on the > receiving side when the migration starts.) Yup. Paolo
