softraid-aware partition editing

[Sam Varshavchik]

I have Fedora installed on (mdadm based) RAID-1 partitions. There are two 
physical hard drives, identically partition table, with the corresponding 
partitions on each drive assembled into a RAID-1 array with mdadm. This 
includes /boot, /, and all other partitions.

I want to resize/move my /dev/md partitions. It's not clear to me how well 
gparted is aware of RAID1. gparted shows me the individual hard drives, and 
the partition layout of each mirrored drive. It does list a "raid" flag for 
each partition, but it's not clear to me if I tell it to resize an existing 
partition, it will mirror the operation on the other partition mirror.

I am considering the following approach:

* Degrade all the partitions. Remove each partition on one of the drives, 
call it drive "B", from its array.

* Use gparted to rearrange the partitions on the other drive, drive "A".

* Take the new partition layout on the "A" drive, and create the 
identical partition layout on the "B" drive.

* Use mdadm --add to add each partition on the "B" drive to its array.

Or is there a better way to accomplish this? If not, I am not clear on a 
couple of details:

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?

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?


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