Hi, On 04/02/11 18:37, MORITA Kazutaka wrote: >> Finally, I see the rather intrusive qemu patch I contributed in the early >> days of sheepdog to allow locking and live-migration to coexist has been >> superseded by the total removal of the sheepdog locking requirement in >> fe14318e31d8. This is a much nicer solution to the problem than mine! Out of >> interest, what happens if several clients do access a vdi at the same time? >> Is it identical behaviour to accessing (say) an iscsi block device from 2 >> hosts, e.g. cluster filesystems can be made to work, or are there weaker >> ordering guarantees on the sequencing of writes and/or problems with >> read-cache consistency that make it less useful? > > Both write ordering problem and read-cache consistency problem would > happen. Sheepdog is not designed to support such situation; all > objects must be one of the following: > - no writer and multiple reader > - one writer and one reader > To use Sheepdog safely, something like a lock system is necessary. > > But this assumption makes Sheepdog much simple and achieves low > latency. Quick follow-up newbie question: does this locking system exist in any way? What _does_ happen if I start two kvm guests using the same image? Cheers -- Leo "costela" Antunes [insert a witty retort here] |