The big piece of copper is fed by redundant rectifiers. Each power shelf has six independent rectifiers which are 5+1 redundant if the rack is fully loaded with compute sleds, or 3+3 redundant if the rack is half-populated. Customers who want more redundancy can also have a second power shelf with six more rectifiers.

I'm going to assume this is on 3 phase power, but how is the ripple filtered?

Inductors and capacitors usually