I know I can simply create a degraded raid array and copy the data to the other drive like this:
mdadm --create /dev/md0 --level=1 --raid-devices=2 missing /dev/sdb1
But I want the specific disk to keep the raw ext3 filesystem so I can still use it from FreeBSD. When using the command above the disk will be a raid disk and I can't do a
mount /dev/sdb1 anymore.
A little background info. The drives in question are used as backup drives for a couple of Linux and FreeBSD servers. I am using the Ext3 filesystem to make sure I can quickly recover the data since both FreeBSD and Linux can read from that without problems.
If someone has a different solution for that (2 drives in raid 1 that are readable by FreeBSD and writeable by Linux), I'm open for suggestions.