Yes, but please provide the clue (was Re: [PATCH] Use new sb type)

[Moshe Yudkowsky <moshe@pobox.com>]

> * The only raid level providing unfettered access to the underlying 
> filesystem is RAID1 with a superblock at its end, and it has been common 
> wisdom for years that you need RAID1 boot partition in order to boot 
> anything at all.

Ah. This shines light on my problem...

> The problem is that these three points do not affect any other raid 
> level (as you can not boot from any of them in a reliable fashion 
> anyway). I saw a number of voices that backward compatibility must be 
> preserved. I don't see any need for that because:
> 
> * The distro managers will definitely RTM and will adjust their flashy 
> GUIs to do the right thing by explicitly supplying -e 1.0 for boot devices

The Debian stable distro won't let you create /boot on an LVM RAID1, but 
that seems to be the extent of current RAID awareness. Using the GUI, if 
you create a large RAID5 and attempt to boot off it  -- well, you're 
toast, but you don't find out until LILO and grub portion of the 
installation fails.

> * A clueless user might burn himself by making a single root on a single 
> raid1 device. But wait - he can burn himself the same way by making the 
> root a raid5 device and rebooting.

Okay, but:

> Why do we sacrifice "the right thing to do"? To eliminate the 
> possibility of someone shooting himself in the foot by not reading the 
> manual?

Speaking for clueless users everywhere: I'd love to Read The Fine 
Manual, but the Fine md, mdadm, and mdadm.conf Manuals that I've read 
don't have information about grub/LILO issues. A hint such as "grub and 
LILO can only work from RAID 1 and superblocks greater than 1.0 will 
toast your system in any case" is crucial information to have. Not 
everyone will catch this particular thread -- they're going to RTFM and 
make a mistake *regardless*.

And now, please excuse me while I RTFM to find out if I change the 
superblocks to 1.0 from 1.2 on a running array...

-- 
Moshe Yudkowsky * moshe@pobox.com * www.pobox.com/~moshe
  "If you're not part of the solution, you're part of the process."
    				-- Mark A. Johnson