[user5994461]

>>> This person's entire job is managing a few racks of hard drives? How often do you think they're actually going to get called in?

How about every day?

Quick guess how often disks need to be replaced when there are thousands of them. ;)

[Dylan16807]

You can replace disks once a month or less. That's not an on-call thing, even if you do make your $200k admin do that grunt work.

Also for one or two thousand disks I would expect less than one failure per week.