Millions of Facebook accounts are a pretty harmless size metric. DBA workload increases with the number of employees, which is proportional to support requests,

Millions of Facebook accounts are a pretty harmless size metric. DBA workload increases with the number of employees, which is proportional to support requests, accidents, changes, strange needs that need to be addressed, and so on. Buying and provisioning disks before space runs out is a small part of a DBA's job, and a modest constant-size task compared to predicting how fast space is running out.