RAID is not backup … really …

A customer with a RAID6 and RAID1 OS drive just had what amounts to an epic failure. 4 drives gone. These are pretty good drives, not a known bad batch. Data points to environmental issues (heat). They don’t understand it, given the nice AC in there, but looking at the drives, a number of them were warm. We have fans doing a pull across the drives, they shouldn’t have been as warm as they were. Customer noticed that the fans had popped out (they had been firmly in place on our last visit and inspection … it takes some significant force or jarring to remove them … they don’t just pop out)
RAID6 was toast. We tried recovery to no avail. Saw some data signatures, but not enough to meaninfully recover it.
The bad side was that the customer didn’t have a backup of all of their data. There was an increase in entropy in the universe … data was destroyed.
They expressed disbelief that RAID would allow them to lose data.
Folks, if you are not backing your data up … if you are not making copies of important things, you are (massively) increasing risk of lossage.

RAID is not backup. It buys you time to get things fixed. It isn’t a backstopping method. Thats what a backup is. Redundancy is good, resiliency is no replacement for redundancy, but it buys you time. RAID is resiliency. Backup is redundancy.
Backup your data, even if you have RAID. Especially if you have RAID. Don’t get lulled into a false sense of security because you have RAID. Bad environmental scenarios will take lots of disks with them. And without a backup, you can lose important information.