Actually, there is something the file system can do to make journaling safe on degraded RAIDs: make the (checksummed) journal blocks equal to the RAID stripe size. Or, equivalently, pad out to the RAID stripe size each commit. This sometimes leads to awkward block sizes, but while writing to any *one* stripe on a degraded RAID-5 endangers the others, you can write to *all* of them with the usual semantics. That's something that's a good idea for performance anyway, so maybe ext[34] should be more vociferous about it. E.g. check each mount and warn if the journal is mis-sized. Or even change the journal bock size on mount if it starts empty. The other solution, of course, is RAID-1, which I like to use for performance and simplicity reasons anyway. (It's really something of a degenerate case of the RAID-[456] rule.) That's one thing I really like about ZFS: its policy of "don't trust the disks." If nothing else, simply telling you "your disks f*ed up, and I caught them doing it", instead of the usual mysterious corruption detectec three months later, is tremendoudly useful information. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
