Re: Time to deprecate old RAID formats?

[David Greaves <david@dgreaves.com>]

Doug Ledford wrote:
> On Mon, 2007-10-22 at 16:39 -0400, John Stoffel wrote:
> 
>> I don't agree completely.  I think the superblock location is a key
>> issue, because if you have a superblock location which moves depending
>> the filesystem or LVM you use to look at the partition (or full disk)
>> then you need to be even more careful about how to poke at things.
> 
> This is the heart of the matter.  When you consider that each file
> system and each volume management stack has a superblock, and they some
> store their superblocks at the end of devices and some at the beginning,
> and they can be stacked, then it becomes next to impossible to make sure
> a stacked setup is never recognized incorrectly under any circumstance.

I wonder if we should not really be talking about superblock versions 1.0, 1.1,
1.2 etc but a data format (0.9 vs 1.0) and a location (end,start,offset4k)?

This would certainly make things a lot clearer to new users:

mdadm --create /dev/md0 --metadata 1.0 --meta-location offset4k


mdadm --detail /dev/md0

/dev/md0:
        Version : 01.0
  Metadata-locn : End-of-device
  Creation Time : Fri Aug  4 23:05:02 2006
     Raid Level : raid0


And there you have the deprecation... only two superblock versions and no real
changes to code etc

David