At Mon, 21 Nov 2011 05:19:26 -0500, Christoph Hellwig wrote: > > On Wed, Nov 16, 2011 at 09:58:14PM +0900, MORITA Kazutaka wrote: > > > > If we increment SD_PROTO_VER, the sheep daemon should return > > > > SD_RES_VER_MISMATCH error when opening the VDI. > > > > > > And then revert to trying the old protocol revision if it fails? Sounds > > > like that would be worth a try. > > > > Or perhaps it might be better not to support the old protocol in the > > qemu block driver? It will make the code complicated. > > qemu has cache modes with and without a writeback cache, and the modes > without it are absolutely required for supporting OSes that don't > support cache flushing. I would suggest we introduce a new protocol > version, and that version will allow the server and client to negotiate > optional feature bits. The write cache would be the first one, but > things like discard support would also be able to make use of it. Sounds reasonable. Thanks, Kazutaka |