On Sun, July 22, 2007 18:28, Theodore Tso wrote: > On Sun, Jul 22, 2007 at 07:10:31AM +0300, Al Boldi wrote: >> Sounds great, but it may be advisable to hook this into the partition >> modification routines instead of mkfs/fsck. Which would mean that the >> partition manager could ask the kernel to instruct its fs subsystem to >> update the backup partition table for each known fs-type that supports such >> a feature. > > Well, let's think about this a bit. What are the requirements? > > 1) The partition manager should be able explicitly request that a new > backup of the partition tables be stashed in each filesystem that has > room for such a backup. That way, when the user affirmatively makes a > partition table change, it can get backed up in all of the right > places automatically. > > 2) The fsck program should *only* stash a backup of the partition > table if there currently isn't one in the filesystem. It may be that > the partition table has been corrupted, and so merely doing an fsck > should not transfer a current copy of the partition table to the > filesystem-secpfic backup area. It could be that the partition table > was only partially recovered, and we don't want to overwrite the > previously existing backups except on an explicit request from the > system administrator. > > 3) The mkfs program should automatically create a backup of the > current partition table layout. That way we get a backup in the newly > created filesystem as soon as it is created. > > 4) The exact location of the backup may vary from filesystem to > filesystem. For ext2/3/4, bytes 512-1023 are always unused, and don't > interfere with the boot sector at bytes 0-511, so that's the obvious > location. Other filesystems may have that location in use, and some > other location might be a better place to store it. Ideally it will > be a well-known location, that isn't dependent on finding an inode > table, or some such, but that may not be possible for all filesystems. To be on the safe side, maybe also add a checksum, timestamp and something identifying the disk the filesystem was created on. Regards, Indan - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
