I booted to a live linux USB and created a new partition table on each of the drives including the drive with OMV installed so that all devices were unallocated. I then reinstalled OMV, and now I get the following errors when booting:
mdadm: No arrays found in config file or automatically (repaeated numerous times, then the below line, then this line another 12 times)
mdadm: error opening /dev/md?*: No such file or directory
Gave up waiting for root file system device. Common problems:
-Boot args (cat /proc/cmdline)
-Check root delay= (did the system wait long enough?)
-Missing modules (cat /proc/modules; ls /dev)
ALERT! /dev/sdc1 does not exist. Dropping to a shell!
I then logged back into a live usb and ran fdisk -l and there were no md devices listed when previously there were, so it seems that the previous RAID array is now gone and all RAID superblocks are removed from each drive and all drives are listed as unallocated in gparted, but OMV can still see an MD array from somewhere?
Did you try installing with all of the data drives disconnected as recommended?
Same error after reinstalling with only the OMV data drive plugged in, only difference is this line, everything else is the same:
ALERT! /dev/sdb1 does not exist. Dropping to a shell!