Yes. It is my understanding that (at least recent versions) will detect incomplete transactions and simply rollback to the last consistent uberblock in case of trouble.
I'm not completely up to speed with regard to the ODF, Uberblocks and the ZIL; In my recollection the "inspection / selection" of uberblocks had been in realm of manual recovery with zdb only, until lately. If I'm not mistaken a automatic 'regress-to-last-known-good-uberblock' function is new and recent. I'm not quite sure whether that uberblock-based rollback _is being used in the context of_ ZIL transaction recovery, or intended in case the ZIL itself had failed (e.g.: ZIL on ramdisk or ZIL on failed vdev with insufficient redundancy). I suspect it is separate and works even without a ZIL. Note that of course this still means that working without a ZIL or having a loss of the ZIL with a crash/unexpected shutdown of ZFS will result in data-loss. It just won't (easily) result in a corrupted zpool because it will try and find a working uberblock at all times, possibly an older one, lacking the latest changes... So far my ramblings. I'm sure it contains a few handy pointers where to look for more solid info... Seth nxyyt wrote: > Hi, everybody, > > I'm a newbie to ZFS. I have a special question against the COW transaction of > ZFS. > Does ZFS keeps the sequential consistency when it meets power outage or > server crash? > > Assume following scenario: > > My application has only a single thread and it appends the data to the file > continuously. Suppose at time t1, it append a buf named A to the file. At > time t2, which is later than t1, it appends a buf named B to the file. If the > server crashes after t2, is it possible the buf B is flushed back to the disk > but buf A is not? > > Does ZFS keep the consistency that the data written to a file in sequential > order or casual order be flushed to disk in the same order? If the writer > operation to a single file always binding with the same transaction group, I > think the answer should be YES. > > Hope anybody can help me clarify it. Thank you very much! > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
