softraid-aware partition editing

[Sam Varshavchik]

Bruno Wolff III writes:

> 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.

So the question then becomes is if you resize the partition, is gparted 
smart enough to relocate the raid signature, together with the rest of the 
filesystem.

>> 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.

The part about reassembling arrays, that I know. My concern is whether using 
parted on a raid partition is going to mess it up.

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