If I powered down the server and remove one of the HDD can it then be put into another PC or enclosure and have the data on it accessible?
Yes as long as that system is running Linux. You can even boot a live Linux distro on that system if it is running WIndows.omv 4.0.16 arrakis | 64 bit | 4.14 backports kernel | omvextrasorg 4.1.2
omv-extras.org plugins source code and issue tracker - github.com/OpenMediaVault-Plugin-Developers
Please don't PM for support... Too many PMs!