I am running gmirror software raid in FreeBSD and it works great. Today I wanted to add another hard-drive to the server (not raided). After installing the hard drive and when I booted the system it didn’t start. All I got was a prompt and a message that said ”Manual root filesystem specification” like this:
Manual root filesystem specification:
: Mount using filesystem e.g. ufs:/dev/da0s1a ? List valid disk boot devices Abort manual input mountroot>
What to do? Well, I couldn’t mount my gmirror but I could mount one of the drives in my gmirror setup. After some trial and error I remembered that I used the ”new” drive previously in another gmirror raid on another server. The disk therefore had gmirror metadata on it that had survived, so somehow that disk took over my normal raid. The metadata survives most disk actions like formatting, partitioning and such…
The gmirror utility uses on-disk metadata (stored in the provider's last sec-
tor) to store all needed information.
I had to run ”gmirror clear /dev/ad2” (ad2 is the new drive) to remove the metadata from the disk. After that I only had to reboot and the normal raid took over again. It took me some time to solve this very frustrating problem. The solution is pretty simple but there aren’t very much gmirror documentation on the web.