I have got rather confused with my PR4100, 4x WD Red 4TB, RAID5
I had a drive failure (Disk 2) and replaced the drive with a brand new one and left it for a few days and didnt see any issues with that but the thing that confuses me is that the RAID status is degraded with a red light on Disk2 on the front of the PR4100.
The screen says drive status is healthy, the Web UI says drive 2 is healthy as all the rest, smart data is exactly the same for all drives.
I am at a loss of what is going on. one thing is apparent, it seems to not want to rebuild the RAID even though auto rebuild is on, i also tried disabling cloud services and apps