On Tue, 16 Feb 2010 08:14:21 -0500 (EST) Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> wrote: > > > On Tue, 16 Feb 2010, Neil Brown wrote: > > > On Thu, 11 Feb 2010 18:00:23 -0500 (EST) > > Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> wrote: > > > >> Hi, > >> > >> I may be converting a host to ext4 and was curious, is 0.90 still the only > >> superblock version for mdadm/raid-1 that you can boot from without having > >> to create an initrd/etc? > >> > >> Are there any benefits to using a superblock > 0.90 for a raid-1 boot > >> volume < 2TB? > > > > The only noticeable differences that I can think of are: > > 1/ If you reboot during recovery of a spare, then 0.90 will restart the > > recovery at the start, while 1.x will restart from where it was up to. > > 2/ The /sys/class/block/mdXX/md/dev-YYY/errors counter is reset on each > > re-assembly with 0.90, but is preserved across stop/start with 1.x > > 3/ If your partition starts on a multiple of 64K from the start of the > > device and is the last partition and contains 0.90 metadata, then > > mdadm can get confused by it. > > 4/ If you move the devices to a host with a different arch and different > > byte-ordering, then extra effort will be needed to see the array for > > 0.90, but not for 1.x > > > > I suspect none of these is a big issue. > > > > It is likely that future extensions will only be supported on 1.x metadata. > > For example I hope to add support for storing a bad-block list, so that a > > read error during recovery will only be fatal for that block, not the whole > > recovery process. This is unlikely ever to be supported on 0.90. However > > it may not be possible to hot-enable it on 1.x either, depending on how much > > space has been reserved for extra metadata, so there is no guarantee that > > using 1.x now makes you future-proof. > > > > And yes, 0.90 is still the only superblock version that supports in-kernel > > autodetect, and I have no intention of adding in-kernel autodetect for any > > other version. > > > > NeilBrown > > > > Hi Neil, > > Thanks for the response, this is exactly what I was looking for and > probably should be put in a FAQ. > I believe the linux-raid wiki is open for anyone to update. Feel free :-) NeilBrown -- 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
