Guys,
Run all my working drives from an LSI 9201-16e in IT mode.
New user of OMV - so after the initial install ran all the available updates - one of which appears to have updated the Kernel from 5.7x to 5.8x
Refer to this Bug report - essentially the system no longer registers the drives as being available.
https://bugzilla.redhat.com/show_bug.cgi?id=1878332
The workaround - confirmed by multiple people (and me on OMV) is to add the following to your Grub.cfg
Craig