Mission-Critical Cooling Tanks: Redundancy Tiers and Reliability Engineering Mission-critical cooling means the tank is part of a system that cannot afford a single point of failure. For data centers targeting Uptime Tier III or IV, the cooling storage must match that redundancy philosophy: separated, concurrently maintainable, and fault-tolerant. This article maps tank design to reliability tiers. A mission-critical cooling tank aligns with the data center Uptime tier: Tier