Water cooling: from innovation to disruption – Part I

One of OVHcloud’s successes is our ability to develop and promote innovation, in both IT and industrial practices. For two decades, we have placed innovation at the centre of our strategy, it’s part of our DNA. We are constantly researching and developing new technologies to optimise the performance of our services.

We manufacture our own servers, we build our own datacentres and we maintain strong, long-term relationships with other technological partners, with a clear objective: to deliver the most innovative solutions with the best price/performance ratio. The most obvious example, and one closely connected to our development, is the idea of using water to cool our servers.

Water cooling at OVHcloud

We began to use water cooling at industrial scale in 2003, even though it went against the conventional wisdom at the time. This technology has allowed us to consistently increase servers’ performance while reducing energetic consumption in our data centers. The challenge was not only to find the right relation between pressure, flow rate, temperature and pipes diameter, but above all to manufacture the solution on a mass scale.

The environmental challenges associated with digital services are of vital concern too, especially for our datacentres. We are very aware of our own environmental impact and we constantly strive to reduce it on a daily basis. After power, cooling servers is usually the most costly activity, electricity-wise, for hosting providers.

Water cooling, combined with an outside air-cooling system, allows us to greatly optimise the Power Usage Effectiveness (PUE) of our datacentres. And less electric consumption means fewer costs for us and our customers, but also a reduced impact on the environment.


Since 2003, we have been developing our own water-cooling system and deploying it in our new datacentres. Our historic customers were the first to benefit from a groundbreaking and highly-effective process on an industrial scale.

Our first generations of water-block technology, were designed by our teams, and manufactured externally. These water blocks had an optimal performance of 60W at 30°C water temperature.

The first generation of water cooling used very simple water blocks, with two copper convex ends crimped together:

On the next iteration of our water blocks, we added some changes to improve reliability and reduce costs:

  • The crimping technology is replaced by brazing
  • Stainless steel push-in fittings replaced the brass-plated ones
  • A cross is also added to the cover to better fix the water block onto the chip
Water block with brazing instead of crimping fabrication technology

In order to facilitate pipe fitting and improve sealing, we again changed the water block technology by introducing compression fittings, which are more reliable and easier to connect.

First compression fittings introduced to the water block technology

A cut view of the water block shows the early thermal hydraulics structure, where the completely smooth base surface forms a reservoir with the cover:

A cut view of the water block


Unlike other providers we maintain complete control of our value chain which means that we can offer cutting-edge solutions at a very competitive price and this is very important to our customers.

During this period, we still designed our water blocks internally and manufactured them externally. The optimal performance for this generation of water blocks is 60W with a water temperature of 30°C.

Our water blocks continued to evolve. We replaced the copper convex end base plate with a simple plate. The cross on the cap was replaced by a cross inside the water block. This allowed us to further reduce the cost of the water blocks without impacting performance.

Copper convex end base plate is replaced by a simple plate which is more cost effective


We always try to be innovative and forge our own path. Since 2013, we have continuously rethought our water-cooling technology, improving performance, operation and cost. This constant innovation allows us to keep up with our customers’ ever-growing demands for increased computing and data-storage capacities, and the ever-increasing amount of heat generated.

The water blocks created in this period were completely different from earlier generations. We replaced welding by screw-based tightening, and the convex top plates were replaced with plates with integrated water inlets and outlets.

2013-2014 generation water blocks

Other factors

At this stage, we began to make water block variations, for example adapting them to the smaller GPU form-factors:

GPU water block

Here you have a side-by-side comparison of the standard, CPU water block, and the more compact GPU water block:

CPU (left) and GPU(right) water blocks

We also developed several special water block designs, adapted for specific constraints:

Special designs of water blocks for specific constraints

A good example is the water block we developed for the high density IBM Power 8 CPUs. In the next picture you can see this special water block’s cover and base plates:

Water block’s cover and base plates used on high density IBM Power8 CPUs

2015 and beyond

The previous paragraphs described our water block technology in 2014. Since then we have come a long way. We have used new technologies like 3D printing, and made some fundamental changes to the design.

In the coming weeks we will publish the next posts in our water-cooling series. These will tell the story of how our water blocks have evolved since 2015. We will focus on the current generation and give you a sneak peek of the improvements to come.

Keep an eye out for our next post to learn more about OVHcloud water cooling!

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Ali Chehade is a Doctor of Engineering in Fluid Mechanics and Thermal Energy. With 12 years of experience in R&D/Engineering, he has worked in the innovation of DC cooling systems and industrial facilities. He has led projects dealing with their thermal performance and energy saving and has implemented techniques/strategies to make them environmentally friendly. Within OVHcloud Ali, as head of R&D-Cooling for 7 years and surrounded by a dozen of engineers, promotes and coordinates the development of solutions to improve the construction and energy performance of DCs.