Saturday, November 26, 2022

Comparing Water and Immersion Cooling for Servers

I recently visited Lenovo, which claims, with a solid foundation, to be a leader in water cooling. It is hard to argue with that position, given Lenovo is aggressive in implementing this technology. 

I was at Dell Technologies World recently and was also impressed by Dell’s joint effort with Intel and GRC to create a better immersion solution for servers.  

I’ve covered water cooling for a long time and have not only built my own water-cooled PCs, but also explored the use of waterless coolant for automobiles. What fascinates me about these technologies is that they can be both far more effective and arguably more affordable than air cooling when you are pushing performance.

Let’s contrast leading water-cooling efforts, like those from Lenovo, with the immersion efforts of Dell, GRC, and Intel

See more: The Server Market

Water cooling

Water is the most effective, affordable coolant at scale. Its ability to pull and transfer heat is largely unmatched in the market, which is why it is aggressively used in both internal combustion engines (ICEs) and electric vehicles (EVs). However, for racing, waterless coolant is often favored, trading off thermal capacity for thermal range and protection against boilover. Water is cheap, common, and effective. 

However, water also conducts electricity, can be corrosive, causes rust, and requires substantial plumbing to bring the water to the components that need it without shorting out the server or PC using it. This piping can make it difficult to service the related servers, because you must remove and replace much of the piping without causing a leak. 

One of the biggest disasters I was involved in was a power shortage that caused an overpressure problem on our water-cooling system. It caused massive flooding in the server and networking room and wiped out data services for half of the country. 

While most companies only cool the processor and GPU, Lenovo has moved to cool all the servers’ heat-sensitive parts, providing a far higher benefit, both in terms of potential peak performance and reliability, because heat is a server killer. Fully cooled servers tend to be quieter and don’t need the level of air conditioning typically required for air-cooled servers. Lenovo uses warm air water cooling, which is far cheaper than cold water cooling and has similar performance benefits.  

While quieter because fewer fans are needed, some parts of these solutions are still air-cooled, meaning you still need to treat the air in the computer room to reduce problems of air contamination and that means you still need to have air-conditioned computer rooms. That’s fine for new buildings but can be problematic for properties that were built with rooms too small or without them at all.  

Immersion cooling

Immersion doesn’t use water. Instead, it uses a petrochemical solution that doesn’t conduct electricity. It doesn’t require the piping of a water-cooled system, but, ideally, and this is the reason behind the joint Dell, GRC, and Intel effort, needs heat syncs designed for liquid rather than air to assure the elimination of hot spots. 

Advantages include the use of sealed cases that allow you to place the servers anywhere there’s power and the need for the server’s capabilities. You don’t need to retrofit buildings with server rooms, but you may need to pipe the liquid outside the building to reduce the load on air conditioning systems. But if you do, it should reduce substantially the electricity needed to cool the building. Currently, immersion doesn’t lend itself to large plants, like supercomputers, and is more ideal for edge computing, particularly where the environment would damage the servers.  

Service is easier with immersion systems than with heavy water cooling, because you don’t need to deal with the piping. However, you do need to deal with the liquid that surrounds the servers. Solutions like GRC’s have reservoirs to keep that liquid off the floor, and technicians would need towels and other tools to deal with the liquid retained by the servers being serviced. While not a huge problem, immersing a server in liquid seems riskier than it is, so folks that haven’t seen current generation solutions are nervous about this approach.

See more: GRC and the Latest in Immersion Cooling

Water vs. immersion

Warm water cooling, which is what Lenovo advocates, and immersion, which is what Dell, GRC and Intel are exploring, both provide similar benefits regarding performance and reliability. 

Warm water cooling may be better for existing or planned server rooms and to add additional capacity to server rooms that are at or over the room’s thermal capacity. 

Immersion, on the other hand, is better where there are no server rooms and especially where the servers must be placed in areas where the environment requires a sealed solution but where the budget doesn’t include a sealed room. With immersion you have a way to provide the environment and security to servers that meet or exceed what you could have with a secure server room without the need to build one.  

Immersion is being underutilized where it would be most valuable for edge computing, and water cooling should be the standard for server rooms both young and old. In the end, air cooling has better alternatives. Consider warm water cooling for your data centers, and immersion cooling for your remote sites to substantially increase reliability and lower costs.

Both technologies report power savings up to 40%, depending on implementation. 

See more: Top Rack Servers

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