Ivan Voras <[EMAIL PROTECTED]> writes: > Christian Laursen wrote: > >> Journaling also needs writes to be done in the correct order. You don't >> want to write the real update to the filesystem before you have made sure > > Ok, but journal is (or should be) protected by checksumming or some > kind of record markers, so invalid entries are not replayed.
That is not the issue. Recognizing valid journal entries should be easy enough. Consider the following sequence of events: 1. Data A is written to the journal 2. The journal is flushed to disk 3. Data A is written to the filesystem Now consider what happens if the disk is reordering writes: 1. Data A is partially written to the journal 2. Data A is partially written to the filesystem 3. The system crashes You now have an invalid journal entry for data A which will not be replayed and some unkown amount of the data is already written to the filesysten possibly leaving it in an inconsistent state. -- Christian Laursen _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[EMAIL PROTECTED]"
