Are there any know problems with a RAID 1 logical volume created with 2 different HD? We originally have 9 FUJITSU 70G (MAP3735NC) drives, but now Dell has replaced 3 of them with 2 140G SEAGATE ST3146707LC and 1 280G FUJITSU MAT3300NC. These larger drives are now mirrored with the older 70G drives.
Why not back up your data, create a RAID 1 with the two larger drives, and restore to that drive? RAID 1 defaults to the capacity of the smaller drive, so rather than maintaining an image of the original 73GB drives (assuming you swapped in the drives one at a time and let the RAID 1 set rebuild), you could double your capacity.