I like the guide for (re) installing of OMV although I just succed to backup my system drive w clonezilla.
I saved my omv config.xml in case with some problems w restoring the clonzilla image back to the system drive.
I assume that after the successfull (re)installing of OMV I can copy config.xml to /etc/openmediavault/ and
I have my old setup back and running.
I mention this here bcs. this last step is not mentioned in the guide, although I hope it is plausible.