Hey, you might want to delay upgrading from 2.0 to 3.0. I've been testing 3.0 for awhile now and there still seems to be "issues". I did the latest upgrade to 3.0.69 and all my Rsync jobs disappeared. This update appeared to create some problems in OMV 3 with the definitions of local and remote shares. (As of the 69 update, UUID's connect under /srv versus /media)
With all the issues noted, I dropped back to 3.0.68. (Backup is a good thing.)
Even in 3.0.68 versions and lower, I can't get access to the data in Samba shares from Windows Clients, at all. This might affect what you're trying to do. It might be best to wait until 3.x is a bit more mature. Your call.
OMV 2.0 doesn't have any of the above mentioned problems. Oh, and I noted on the forum that someone mounted a foreign volume from OMV .5 in a OMV 2.0 machine, but he didn't mention what he did with permissions. (CHOWN?) He was just after the data files.