We have a PR2100 with latest firmware comprising two each 2TB WD Red drives.
WE noticed from the log files that on Sunday October 27, the drive reported a failed raid configuration due to power outage. In addition, the disk reported Full at RAID 5 with all drive lights solid red.
The GUI display shows 0Kb but logging via cli with ssh shows the raid disks with relevant sizes.
It is possible to rebuild this RAID without data loss?
See or move your post to the correct subforum for your device where users more familiar with your device may be able to assist. The My Cloud subforum generally covers the single bay/single drive second generation My Cloud.