I just installed a new Hardware RAID card in my microserver (gen8), and as soon as I booted it gave me this error and refused configuration of the Raid arrays on the P222.
It seems related to the battery which is connected to the cache module on my card. The battery was empty when I first booted the system.
Solution was to power up the system, leave it in POST while the battery was being charged.
After about an hour I tried again and I was able to clear the cache, clear the configuration for the RAID array and create a fresh array on the controller.
Note; perhaps the period of an hour could be shorter or longer in your specific case. The battery provided with my unit was quite small so it was charged enough after an hour to continue without errors. But I guess that that might differ per unit.
Note; Several posts on HP and server forums were suggesting that the unit might be defective and said to return the battery / cache module / Smart Array card.
This post is mostly here to encourage patience; Getting a cup of coffee and checking again after an hour was the solution in my case.