In the past, big size external USB HDs used to come with AC Power.
These days, I can get 4TB USB HDs without AC Power although 5TB or bigger HDs still comes with AC adapter.
For Servers which may have two or more external USB hard drives attached for backup purposes, would you recommend AC Powered or just go with portable units that draws the power from USB ports?
Does it make any difference?
"my inner sysadmin is also asking about using a USB drive for backup at all. " --> are they suggesting NAS instead of USB?