>The only way to guarantee consistency in the snapshot is to always >(regardless of ZIL enabled/disabled) give priority for sync writes to get >into the TXG before async writes. > >If the OS does give priority for sync writes going into TXG's before async >writes (even with ZIL disabled), then after spontaneous ungraceful reboot, >the latest uberblock is guaranteed to be consistent.
This is what Jeff Bonwick says in the "zil synchronicity" arc case: "What I mean is that the barrier semantic is implicit even with no ZIL at all. In ZFS, if event A happens before event B, and you lose power, then what you'll see on disk is either nothing, A, or both A and B. Never just B. It is impossible for us not to have at least barrier semantics." So there's no chance that a *later* async write will overtake an earlier sync *or* async write. Casper _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
