OMV.data.Store.ImplicitModel-ext-1057-7 error adding a RAID disk

I have been trying to add a single mirrored disk to Open Media Vault and been getting:

Error adding RAID disk

In my case the new disk was created using a Debian live USB disk. I think this was the problem. So I booted to OMV and looked at the mdadm config file in Debian:

The config file can be found at:

/etc/mdadm/mdadm.conf

The problem I suspect was that the new disk was also “/dev/md0”, so I commented the line out:

ARRAY /dev/md0 metadata=1.2 name=nas2:RAID1Mirror UUID=a77b4c17:6ddd1afc:58bf7cdd:a51275ef

Then I restarted and the new disk showed up.