Alan Farrimond, Vice President of Knowledge Middle Options at Wesco, believes the rise of AI is driving high-density calls for that conventional air-cooling alone can’t deal with – as he explains the 4 crucial strategies groups ought to take into account.
The rising want for high-density information centres to assist AI and different demanding workloads is driving extra information centre groups to undertake liquid cooling somewhat than extra conventional air-cooling strategies for the IT crucial load. However outdoors of hyperscalers, many information centre groups are nonetheless studying the completely different liquid-cooling strategies that exist and the way they’ll be sure that deployment goes easily.
There are 4 base design choices for liquid cooling to contemplate: conventional scorching/chilly aisle containment, rear-door warmth exchangers, direct-to-chip cooling, and immersion cooling. The latter three choices far outperform conventional air-cooling programs, which can be inadequate for cooling the power-hungry racks in high-density information centres by itself.
Every of those choices has its personal distinctive efficiency ranges and deployment and upkeep calls for that should be thought of.
Let’s discover every of the liquid cooling choices and what information centre groups ought to be fascinated with to allow them to select the precise choice for his or her undertaking.
Conventional cold and hot aisle cooling is a extensively used technique in information centres. This system includes arranging server racks in alternating rows with chilly air intakes going through one chilly aisle and scorching air exhausts going through the alternative scorching aisle.
The chilly aisle is provided with cool air from computer-room-air-conditioner (CRAC) and computer-room-air-handler (CRAH) models, whereas the new aisle collects the heated air and returns it to the cooling models for re-cooling. This separation helps to forestall the blending of cold and hot air, thereby bettering cooling effectivity and lowering power consumption. Nonetheless, this system is mostly restricted to circa 15-20kW per cupboard.
2. Rear-door warmth exchangers
This know-how is often utilized by information centres which can be switching to liquid cooling as a result of it offers an environment friendly and full cooling resolution.
Rear-door warmth exchangers sit on the again of a cupboard and seize scorching air from IT gear earlier than it enters the white house. The captured warmth is transferred through a coil to a relaxing water supply, and the warmth is then discharged out of the again of the cupboard.
A advantage of rear-door warmth exchangers is that they typically can take away 100% of the warmth generated by the server with out requiring different heat-dissipating applied sciences. They’re additionally room impartial. The temperature of the air discharged from the cupboard would be the similar because the room’s ambient temperature.
Rear-door warmth exchangers usually assist energy densities as much as 85kW to 90kW per rack. Some producers state their know-how can assist as much as 200kW, however these choices are sometimes designed for specialised use instances or cupboards. When contemplating rear-door warmth exchangers that declare to assist above 90kW, confirm that they’re acceptable for the appliance and cupboard the place they’ll be deployed.
3. Direct-to-chip cooling
This cooling technique, also referred to as direct liquid cooling, places water immediately on a warmth sink or chilly plate contained in the gear to take away warmth at its supply, earlier than it’s discharged as scorching air.
There are two choices for direct-to-chip cooling. The most typical is single-phase cooling. Right here, the coolant or water that has absorbed the IT gear’s warmth is moved to a coolant distribution unit (CDU), which transfers the warmth to a bigger loop. The cooler fluid is then pumped again to the {hardware} as a part of a steady cycle.
Within the two-phase choice, the liquid that absorbs the warmth is boiled off. The ensuing vapor then condenses again right into a liquid and cycles again by means of the system.
Direct-to-chip cooling sometimes helps as much as 100kW per rack, though in some instances it could actually go as excessive as 120kW. A trade-off of this cooling technique is that it solely cools the chip, not the remainder of the cupboard. Which means one other cooling resolution like rear-door warmth exchangers must be used. As it’s not a full-cabinet cooling resolution, it’s sometimes not the primary selection as a cooling resolution.
4. Immersion cooling
Totally submerging servers or racks in liquid is the ultimate closed-loop liquid-cooling choice.
This course of makes use of an inert and non-conductive dielectric fluid in an immersion enclosure to soak up warmth generated by servers, GPUs and different related {hardware}. The heated fluid is then circulated from the enclosure to a cooling system the place the warmth is extracted, corresponding to with warmth exchangers or direct liquid-to-liquid cooling. Subsequent, the cooled fluid is transferred again to the enclosure.
A disadvantage of immersion is that it hinders upkeep. If gear must be repaired, for example, staff have to carry it from the immersion liquid, typically utilizing a gantry, after which look forward to it to dry. This has largely restricted the usage of immersion cooling to functions like bitcoin mining the place the {hardware} doesn’t expertise common change and sustaining gear just isn’t a excessive precedence.
The upkeep ache level may be addressed with a two-phase choice for immersion cooling. This strategy makes use of a dialectic liquid that boils off because it captures the warmth generated by the gear. The vapor that’s produced is then captured, condensed and cycled again by means of the system (or not, if upkeep must be accomplished). Nonetheless, the two-phase immersion choice remains to be early in its adoption part.
Different concerns earlier than deploying
After a knowledge centre group decides on a liquid cooling strategy, protecting a couple of issues high of thoughts throughout planning and implementation will help them keep away from surprises.
First amongst them is to plan for your complete system, not simply the know-how.
Typically, information centre groups cost forward with constructing and buying a invoice of supplies for a liquid-cooling undertaking earlier than they perceive what will probably be wanted to make these supplies work collectively. This may create roadblocks after they uncover the set up contractor they employed isn’t accustomed to making a secondary water or fluid loop, which is required to take away warmth masses and is separate from the first loop that cools your complete facility.
Addressing the day-two concerns for a liquid-cooling system can also be necessary. Gear just like the CDUs utilized in direct-to-chip cooling programs are far much less tolerant of contaminants than the CRAC and CRAH models which were utilized in information centres for many years. Knowledge centre groups now want to consider contamination that may occur on the microscopic stage, corresponding to through the use of components like inhibitors that assist stop bacterial progress.
Groups also needs to be fascinated with how they’ll standardize their liquid-cooling system if their scope extends past one information centre.
That is the place a provide chain accomplice with a large attain and liquid-cooling know-how may be particularly useful. They will help create a foundation for design that features not solely stamp-ready drawings but additionally set up and commissioning packages, basically making a playbook for each deployment. This may save vital time, effort, and cash in comparison with treating every liquid-cooling deployment as a bespoke undertaking.
Preserve cool and keep on
Rising energy calls for are making liquid cooling a necessity in in the present day’s information centres. By understanding the nuances of the completely different liquid-cooling choices, information centre groups can select the most effective cooling technique for his or her facility and handle the dangers that include bringing liquids into the white house.
