softraid-aware partition editing

[Bruno Wolff III]

On Sun, Dec 13, 2009 at 23:26:29 -0500,
  Sam Varshavchik <mrsam at courier-mta.com> wrote:
> 
> 1) Does an ext3 partition running on top of a RAID-1 layer "look"
> any different on disk than a native ext3 partition? There's
> obviously a "raid" flag shown by parted, that comes from somewhere,
> but from parted's perspective, is a non-RAID-1 ext3 partition any
> different than a RAID-1 partition? In other words, if I tell parted
> to resize a RAID-1 ext3 partition, am I going to get mangled
> results?

The raid header version that is currently used by default in Fedora is
at the end of the partition. So the file systems look like normal file
systems. If gparted is detecting raid, I would guess that it is getting this
from the partition type byte.

> 2) Does creating a partition of "Linux raid autodetect" is all I
> need to do in order to succesfully add it to a degraded RAID-1
> array, and have the array rebuilt and synced up?

You want to do something like:
mdadm /dev/md0 -a /dev/sdb1
using the correct device names for the raid array and the device you want
added.