mdadm 1.x device naming

[Colin Watson]

I've been looking at Felix's raid branch which adds support for mdadm
metadata version 1.x, and trying to bring it up to date.  The first
thing I noticed was an issue with device naming.  With mdadm metadata
0.9, md devices were just numbered.  Easy.  With mdadm metadata 1.x,
devices can also be named, which gives you things like /dev/md/home.
(There's also a "homehost" quirk for arrays that can be attached to
multiple hosts; I propose to ignore this for now.)

In many ways this is better.  Named devices means that you're not
relying on enumeration which means that devices aren't going to move
around, which is always good for GRUB.  Thus, I don't think we should
invent an enumeration scheme and I certainly don't think we should
require entries in device.map to map /dev/md/home to (md0), or whatever;
that just takes us back to the bad old days.  However, we do need some
way to name the device in GRUB.

Does anyone object to this simple scheme?

  /dev/md/NAME => (md/NAME)
  all other md device name formats as before

As far as I'm aware, we don't use slashes in GRUB device names right
now, so this is a bit novel; but I wanted to minimise the chance of
clashes and confusion, and I don't believe using a slash should actually
do any harm.

Thanks,

-- 
Colin Watson                                       address@hidden