Consensus and confusion in liquid cooling maintenance

Over the past few years, the buildout of high-density data center space for generative AI hardware has led to the deployment of direct liquid cooling (DLC) at an unprecedented scale. This represented a growth of DLC technology out of smaller, specialized supercomputing applications at a rate that outpaced the development of standards and best practices for operating liquid-cooled data center environments. The chief growing pain for DLC was fragmentation in technical details: in system designs, coolant chemistry, resiliency approaches and maintenance procedures.

Accumulated experience from these early years of large-scale DLC has started to converge and produce some identifiable trends in operator preferences to address these problems. Data center operators and IT OEM partnerships tend to favor water cooling systems (specifically with 25% propylene glycol, PG25) over other DLC types for the next few years, though expectations for the longer term are less clear. Recent DLC deployment has trended toward larger (hundreds of kilowatts or megawatt-scale) coolant distribution units (CDUs), often in redundant arrangements to serve rows of IT racks, and operated by facility staff. This suggests growing confidence in one approach to divide maintenance responsibilities between facilities and IT teams, though it is not the only approach being used.