This is generally nothing that needs to be worried about. "PD 20" is generally the backplane.  If you are still concerned with it, I'd recommend that you make sure your backplane and PERC firmware/driver is up to date. I'd also suggest double checking OpenManage to make sure you aren't reading any issues on the drives and to double check the status of your battery.
Hello, One of my clients PowerEdge servers had an unexpected shutdown over the weekend. It came right back up after a few minutes, VMs were all running, etc. I checked the logs and noticed it had an error that read: Controller event log: Unexpected sense: Encl PD 20 Path 5842b0b045d63200, CDB: 12 00 00 00 04 00, Sense: 5/24/00: Controller 0 (PERC 6/i Integrated) Is this error something to be concerned about? Just want to make sure the server isn't dying or something. Thanks!
PowerEdge R610 -- Controller event log: Unexpected Sense error