Installed OMV 3 beta image on microSDcard (128GB, SanDisk, UHS-I), booted it with RaspBerryPi 3B, did apt-get update, upgrade, dist-upgrade and then ended up with an up to date system; Erasmus 3.0.24
In OMV web admin under Storage > Physical disks
it actually says the disk is 119.08GB so that should be OK.
However, under File systems this is what it shows:
and I can't resize or do anything (gui doesn't respond to actions, only mounting works). Rather disappointing, but hey, it's a beta. I'm inclined to do a RPi debian install image, and then maybe try OMV on top of it, because this didn't happen with a debian install on the Pi (had it on this Pi before).