Cache device missing in btrfs pool.

[Fffrank]

Finally getting back to a limp after what I now must assume was some kind of power-surge or lightning strike.  

 

Replaced my server mainboard.

Then discovered that my H220 HBA had also failed. I replaced that.

 

As soon as I was able to boot I heard a drive that was clicking and knew right away it was dead.  Sure enough cache won't come up because a drive has disappeared (disk information shows it has failed SMART but I don't even have the ability to see it on the main screen.)

 

I left that slot unassigned and brought the array up.  I thought a btrfs pool should still come up but received an error that it was unmountable.  I do have extra drives in the system that I can try to substitute but don't want to screw anything up. What do I try next? 

[JorgeB]

Please post the diagnostics and the output of

btrfs fi show