EX4100. I had disk 4 (WD Red 3TB) fail and replaced it. I’m running RAID5 set to Auto Rebuild. Inserted new disk expecting it to re-build - nothing happened. Checked online and seemed a manual rebuild was the way ahead. Did that. Message saying re-build was going to take literally thousands of minutes. Now I have four red lights on all drives. I can’t see any shares but can see users. System says there is no RAID configured. Drive 1 gives no info re temperature etc, as though that has also now failed. Before mild panic turns into a steady state, does anyone have experience of this?