I have 2 500gb drives in a RAID1 setup that I needed to upgrade for more space. I mdadm --fail'ed each drive in turn and I used dd to copy each drive to it's respective larger drive (2tb each), removed the smaller drives and replaced them with the larger drives, and reassembled the array and forced a resync. So now I've got a 500gb RAID1 sitting on 2TB drives, and wish to grow them.
The plan is to use mdadm --manage /dev/md0 --grow to grow them, then boot a rescue cd, assemble the array under that environment, and do the resize2fs on them. Can I use mdadm --grow on a mounted and live filesystem? Also, do I need more options to make sure the grow operation stays raid1?