Haydn Solomon wrote: > I see that vmware just demonstrated migration of virtual disks. I know > that kvm is very young but I think has come a long way in a very short > period. I just wanted to get some feedback/discussion on how difficult > this would be to implement in kvm/qemu and if this would be anywhere > in future plans for development? Would this be less complicated than > live migration of memory?
Disk migration is super easy to implement in KVM. There are two basic models you can follow to do disk migration. In a push model, you would apply a similar algorithm to the memory migration algorithm whereas you pushed the whole disk over in chunks keeping track of what bits on disk have been dirtied. You'd converge after a certain number of iterations and then perform the memory migration. A pull model would immediately do the memory migration and allow QEMU to continue running on the source node acting as an IO server. Any disk IO from the guest would either go directly to disk if the block was present or would be fetched from the QEMU instance on the source node. The only trick here is that you'd want to continue transferring blocks even when the guest isn't accessing the disk. The push model may require parallelization of the disk and memory convergence depending on how much disk activity the guest is doing. That's a pretty interesting problem but it shouldn't be too hard to solve. The push model has the advantage of having the smallest performance impact over time. The pull model has an advantage of immediately reducing CPU usage on the source node at the expense of a potentially severe degradation in performance of the guest. Both models probably require roughly the same amount of time for migration completion. Very good thing for someone looking for a fun task in KVM :-) Regards, Anthony Liguori > ------------------------------------------------------------------------ > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio 2005. > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ > ------------------------------------------------------------------------ > > _______________________________________________ > kvm-devel mailing list > kvm-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/kvm-devel > ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
