Il 18/12/2013 11:24, Orit Wasserman ha scritto: >>> >>> For live migration we need the sync option (async ignores O_SYNC and >>> O_DIRECT sadly), >>> will it be supported? or will it be the default? >> >> Since this is bypassing the client kernel FS I/O layer question around >> support of things like O_SYNC/O_DIRECT are not applicable. >> > > so no live migration support?
No, live migration just works. O_SYNC is not used anymore in QEMU, we just issue a flush after every write. And all protocol drivers except files/block devices _always_ bypass the kernel page cache (libiscsi, NBD, ceph, and now libnfs) so they are always behaving as if they had O_DIRECT. For these protocols, cache=writeback and cache=none are entirely the same. Paolo
