I have the same motherboard (REV 2.0 F1) and the same Supermicro AOC-SASLP-MV8 (.21 firmware) card.
I had the same issue as you did at almost the same time (today vs a few days ago for you). I was hoping someone found a good solution. The way I "fixed" was to set the OnChip SATA type to "NATIVE IDE". This is not as good as AHCI (I believe), but now I have access to all my drives. Of course you will have to remap some of your drives since, some will now look like IDE drives to UNRAID.
So far the performance seem about the same. Did a random file copy of 10 gigs and seemed to be about as fast as before.
Hope this helps and if you find something better, let me know.
