Hi all

So, we have MD3820f which shows the error.

Cache Backup Device Failed.
Component reporting problem: Cache Backup Device (USB 2). Status: Failed.
Location: RAID Controller Module 1, enclosure 0, device slot USB 2.

In the storage system profile i can see that status for one of the two devices is failed.

Recovery Guru Suggests that Cache Backup Device is replaced..
But Dell does not supply a Cache Backup Device (it's a 16GB M2 flash card).

I got the advice to reseat the Cache Backup Device, so i did.
Controller put offline. Cache Backup Devices Reseated. Controller put online again.
Problem still persist.
Then got advice that controller needed replacement, so we did. 
Everthing went fine, new controller adapted firmware, NVSRAM and config.

Controller now shows, that both controllers have both Cache Backup Devices in Optimal state.

But recovery guru still reports: Cache Backup Device Failed. Unable to retrieve detailed information.
And i am not able to activate "Recheck" that is, nothing happens, The "Turning Gears" does not appear, like the normal do, during a recheck.

I did clear the event log, but no difference.
Firmware is latest 08.25.14.60

Any suggestions on how to proceed?

Best Regards
Claus