Counter anecdata: I've got a Ceph cluster running on multiple RPi 4s using external Seagate 4 and 5 TB portable hard drives. So far zero issues for about 1 year since I bootstrapped this cluster..

I use a combination of official RPi 4 power supplies and an Anker 6-port USB power block that I'm pretty sure tops out at less than 3 amps.

More importantly, everything is plugged into APC UPSes.