Ceph is incredibly reliable. I run a ~ 250 PB Ceph install with the equivalent of 1.5 medium-paid full time engineers[0], and I sleep very well at night.

Failure after hardware failure, it just keeps running and running. We currently fail at a rack level, but no reason we can't do that at a building level with enough hardware.

0: We have more people on our team, but we also deal with other things that take a lot more of our time.