Blockchain is a decentralized database technology that tries to approach very important questions in a different way to traditional (centralized) databases. Ultimately, these questions boil down to:

• What is the truth?
• Who gets the last word on what the truth is?

In information management circles, we’ve tried to find a way to the ‘single source of truth’ for decades. Information sprawls. Being able to have a definitive answer on any one matter – whether that’s the last version of a memo or the real-time stock in a retail store – is incredibly valuable.

After all, if you’ve worked in an office for any length of time, you’ve probably renamed a file to something like ‘version 2.5 final final THIS ONE’ – and inevitably, it’s not ‘final’. This analogy doesn’t quite work because blockchain isn’t a file storage technology, but we’ll come back to that later.

Blockchain’s answer to defining truth is democratic. As its name suggests, information is stored in blocks, and these blocks are linked together in a chain. The order of this chain is documented, so once a change is made, it becomes an indelible part of ‘history.’ This establishes ‘truth’ by tying historical facts (or transactions) together so that one is linked to the next – and altering one event means altering the entire chain of events, rather like needing to rewrite an entire history book from the change of one small detail.

Let’s look at an example in practice.

When a change occurs in a blockchain network (like buying a cup of coffee with cryptocurrency) the information is sent to the network and preliminary checks are done – for example, checking that you have enough money to buy the coffee.

If there are any blockchain experts reading this, let’s assume it was a very expensive and significant coffee, because smaller transactions are often handled slightly differently in blockchain, in what we call Layer 2 Networks. We’ll come back to these later in the series.

Once the transaction has been verified, it’s then packaged up with other transactions to form a block and linked to the previous block in turn.

Next, the network has to make sure that the block is valid. This is done through a process called consensus, or validation, and is handled slightly differently depending on the network. Bitcoin uses a system called ‘Proof of Work,’ where different users work to verify complex equations that prove that the block’s contents haven’t been altered and that it does really link to the previous block. If anything has changed in the block since it was submitted, the equation doesn’t work and the block is rejected.

This is a computationally intensive process and requires a lot of electricity, particularly at scale. At one point, Bitcoin used as much electricity as all of Norway, so there are many other alternatives. For example, Solana uses ‘Proof of Stake,’ where the parties involved in verifying the block put forward assets (in this case, actual cryptocurrency). Then, the lead validator builds the block and adds a digital signature to it so as to say that they checked it, and that they have a real stake in the matter (i.e. money). This data is then re-checked by other validators, who vote on the validity. If there are enough ‘yes’ votes, then the block is agreed upon.

Of course, this does rely on trust, but there are usually big penalties for validators who ‘cheat.’ For example, they can have their stake removed, and/or they can be restricted from contributing to validation in future.

Solana also uses a system called ‘Proof of History’ to help it process a large number of transactions, which is a bit different to other systems.

But once approved, the block is then officially part of the chain, and the transaction can be completed – and you can get your Americano.

To define blockchain in another way: it creates a system of establishing trust and control without one single authority. Trust is distributed between all the different parties involved in the network. In fact, almost anyone can become a blockchain validator, although each network has its own requirements to do so.

As we’ve seen, blockchain is much bigger than just Bitcoin; the distributed database structure can be applied to all kinds of settings. We’ve seen organizations using blockchain to verify where tuna fish were caught, to ensure that they were ethically fished, and that the handling of said tuna could be traced from supermarket to distributor, and back to the person who caught them in the ocean.

Another major application for blockchain is in identity verification. Blockchain systems can help to check the validity of something without violating its privacy.

For example, imagine that you’ve discovered the famous Narnia wardrobe. You’ve decided to try to prevent people from sneaking in and causing chaos, so you’ve created a password-protected way to get in. You’re trying to qualify for state support to redevelop your house into a tourist attraction, so you need to prove that the wardrobe is the real deal. On the other hand, you don’t want to just give out the password because you’ll have government officials popping in and out all the time, conjuring infinite amounts of Turkish Delight and smuggling talking badgers out under their coats.

Blockchain’s answer to this is simple: you pop inside and take a selfie with Aslan and Mr. Tumnus, showing conclusively that you have access. This is how Self-sovereign identity works, which requires blockchain to link the wardrobe with the selfie. The two need to be linked – after all, you could have just popped into your friend’s magical wardrobe and taken a photo of some other lion and faun!

Many age-verification systems work in similar ways. For example, in many countries it’s illegal to give credit to someone under 18, so having a credit card is proof that you’re older than this, without having to show your passport or driving license. And in this case, it’s vital to show that the credit card is linked to the person using it, or the system doesn’t work.

Finally, it’s worth knowing that there are a number of different ecosystems within blockchain. Although they’re not strictly specialized, we can generalize that Bitcoin is focused on currency, Solana tends to being more of a platform for decentralized apps, and Ethereum is known for facilitating transactions quickly and making use of smart contracts – an ecosystem similar to Avalanche, but Avalanche has a modular approach focused on speed.

This picture is further muddied by the fact that there are public and private blockchains, which are also subdivided, but which essentially dictate who can see the blockchain and who has permission to be on it.

In our next blog post, we’ll go into a bit more detail about the blockchain world, focusing on the truths that IT leaders need to know. In the meantime, if you want a clearer, more practical view of how blockchain fits into real-world infrastructure, you can explore our resources and customer success stories on our website.

At OVHcloud, we are constantly looking for ways to improve our operations and reduce our impact on the environment. This has been a defining part of the company since 1999 and is a key part of our organisational DNA and our commercial model.

We are very proud to present the new Smart Datacenter cooling system, which significantly improves energy and water efficiency while delivering a significant reduction in carbon impact across the entire cooling chain, from manufacturing and transport to daily operations.

The system is a new way of building and deploying datacenter infrastructure, changing how we manage and monitor water supply and demand, using a combination of industrial design, IoT sensors and AI innovation, specifically in our smart racks, advanced cooling distribution units (CDUs) and intelligent dry coolers.

Smart Datacenter delivers a reduction in power consumption of up to 50% across the entire cooling loop, from server water blocks to dry coolers, and consumes 30% less water compared to OVHcloud’s earliest design, driving major sustainability benefits. The system also uses complex mathematical models capturing detailed rack-level and environmental data to optimize cooling performance in real time. Furthermore, all operational data is fed into a centralized data lake, enabling cutting-edge artificial intelligence to predict, adapt, and enhance system efficiency and reliability.

Let’s get into the detail.

The system has three main components:

1. Smart Racks: These are designed with an innovative hydraulic “pull” architecture, where each rack autonomously draws exactly the water flow, pressure, and temperature it needs, dynamically adapting to server load and performance.
2. Advanced Cooling Distribution Unit (CDU): This is a compact, next-generation primary loop unit that autonomously balances flow and pressure across all racks without manual intervention or any electrical communication. It uses only hydraulic signals (pressure, flow and temperature of water) to “understand” rack demands and continuously optimizes operation for lowest power consumption and extended pump lifespan.
3. Intelligent Dry Cooler: This is operated seamlessly by the CDU, eliminating the need for separate control systems (“brains”) on both the dry cooler and the CDU. This unified control architecture ensures optimized, coordinated performance across the entire cooling infrastructure.

OVHcloud’s new Single-Circuit System (SCS) replaces the previous Dual-Circuit System cooling architecture (DCS), which consisted of a primary facility loop and a secondary in-rack loop separated by an in-rack Coolant Distribution Unit (CDU), installed inline directly after the rear door heat exchangers (RDHX), as shown in Figure 1. The CDU housed multiple pumps, several plate heat exchangers (PHEX), and a network of valves and sensors.

Figure 1. Dual-Circuit System cooling architecture (DCS) vs Single-Circuit system (SCS).

That previous design maintained turbulent flow through water blocks (WBs) using the in-rack CDU to regulate flow and temperature differences, ensuring performance despite OVHcloud’s ΔT of 20 K on the primary loop (far higher than the typical market value around 5 K).

Removing the in-rack CDU — replaced by a Pressure Independent Control Valve (PICV), a flow meter, and two temperature sensors on each rack — simplifies the system to a single closed-loop, where the flow rate through servers is dictated directly by the primary loop, adapting dynamically to rack load density. On the rack side, the system adapts the exact flow the rack requires by analyzing the water behavior and performing iterative, predictive thermal optimization considering IT components and the supplied water temperature and flow. This results in lower inlet water temperatures at the server level due to the elimination of the in-rack CDU’s approach temperature difference, and reduces electrical consumption, CAPEX, carbon footprint, and rack footprint.

To prevent laminar flow and maintain heat transfer efficiency at low flow rates, OVHcloud introduced a passive hydraulic innovation by arranging servers into clusters connected in series with servers inside each cluster connected in parallel, rather than all servers in parallel. This ensures higher water flow through individual servers even when the rack density is low. While this increases system pressure drops depending on cluster configuration, it results in better thermal performance and all servers receive water at temperatures equal to or lower than in the previous DCS design.

The racks operate on a novel hydraulic “pull” principle — where each rack draws exactly the hydraulic power it requires, rather than being pushed by the system. The  CDU then dynamically adapts the overall hydraulic performance of the primary loop, balancing flow and pressure in real time to match the actual demand of the entire data center.

A key breakthrough is the CDU’s communication-free operation: it requires no cables, radio waves, or other electronic communication with racks. Instead, it analyzes hydraulic signals — pressure, flow, and temperature fluctuations within the water itself — to understand each rack’s cooling needs and adapt accordingly. This eliminates complex telemetry infrastructure, reduces operational risks, and enhances system reliability. To ensure water quality and system longevity, water supplied to the data center is filtered at 25 microns, and multiple sophisticated high-precision sensors continuously monitors water quality in real time.

The CDU is 50% smaller than the previous generation and manages the entire thermal path — from chip-level water blocks, through the racks and CDU, to the dry coolers.

The newly designed dry cooler is also 50% smaller than the previous model and features one of the lowest density footprints worldwide. Thanks to years of thermal studies on heat exchangers by the OVHcloud R&D team, it has 50% fewer fans, resulting in very low energy consumption, while also reducing noise. Its compact size means that we can also transport more units in the same truck!  This design achieves a 30% reduction in water consumption compared to OVHcloud’s earliest dry cooler design. A key innovation in the dry cooler is its advanced adiabatic cooling pads system, which cools incoming hot air before it passes through the heat exchangers. This high-precision water injection system is the first of its kind, and adjusts water application based on multiple sensors and extensive iterative calculations, including data center load, ambient temperature, and humidity levels.

Unlike traditional adiabatic systems, the pads’ system does not use a conventional recirculation loop. Instead, water is injected when needed onto the pads via a simple setup consisting of a solenoid valve and a flow meter, eliminating complex hydraulics such as pumps, filters, storage tanks, level sensors, and conductivity sensors. The system maintains water quality and physical/chemical properties through careful design, drastically simplifying operation and reducing maintenance needs.

The CDU continuously analyzes data from up to 36 sensors distributed across the CDU itself and the associated dry cooler. It also collects operational data from solenoid valves, pumps, and dry cooler fans across the infrastructure loop. All components are monitored and managed by the system’s central intelligence—the CDU’s control panel—providing a comprehensive understanding of the entire system’s behavior, from the data center interior to the external ambient environment, ensuring real-time performance oversight and precise thermal regulation.

Through this iterative and precise control of water injection, the system optimizes cooling performance and Water Usage Effectiveness (WUE), ensuring minimal water consumption without sacrificing thermal effectiveness.

Advanced System Analytics, Learning & AI Integration

The entire system is designed to continuously analyze the thermal, hydraulic, and aerodynamic behaviors of the various fluids along the cooling path. It uses daily operational data to learn and adapt its performance dynamically, optimizing cooling efficiency and reliability over time.

The CDU’s brain—the control panel—aggregates data from 36 sensors distributed across the CDU and dry cooler, as well as operational data from solenoid valves, pumps, and dry cooler fans within the infrastructure loop. It also collects critical rack-level information, including flow rates, temperatures, and IPMI data that reflect IT equipment behavior and performance. All this operational data is pushed to a centralized data lake for parallel analysis, which forms the foundation for the next step: integrating cutting-edge artificial intelligence (AI). This AI will leverage the continuously gathered data and learning processes to enhance predictive capabilities, optimize future operating points, and enable fully autonomous decision-making.

This combination of real-time learning and AI-powered analytics will provide advanced diagnostics, predictive maintenance, and proactive management — maximizing uptime, reducing costs, and driving ever-greater sustainability.

Iterative Control System Innovation

The iterative control system manages all aspects in real time, hands-free, continuously learning from sensor data and operational feedback. It applies algorithms to the pump speed on the CDU, the fans on the dry cooler and the solenoid valve controlling water injection on the adiabatic pads.

On the rack side, the system uses a PICV valve, flow meter, and two temperature sensors to adapt the exact hydraulic flow needed by each rack, considering IT load and incoming water conditions, iteratively optimizing thermal performance and energy efficiency.

On the CDU, the system analyzes combined hydraulic signals from all racks alongside ambient data center conditions, dynamically balancing flow and pressure across the entire data center infrastructure without human intervention.

Furthermore, OVHcloud’s cooling system integrates intelligent communication between cooling line-ups to enhance failure detection and simplify maintenance. This is achieved through embedded freeze-gaud and resilience-switch mechanisms that ensure continuous operation and system resilience. The freeze-gaud system is designed to protect the dry coolers in sub-zero ambient conditions by keeping water circulating through their heat exchangers. If the overall loop flow drops below a predefined threshold, the system automatically opens a normally closed bypass valve to maintain circulation—preventing freezing despite the use of pure water (without glycol) as the cooling medium. The resilience-switch system maintains redundancy by hydraulically linking multiple cooling lines. In the event of failure or overload on one line, normally open solenoid valves isolate the affected line, while bypass valves on neighboring lines open to redistribute water flow and maintain cooling performance. This dynamic and autonomous valve management ensures uninterrupted service and rapid fault response.

Drawing inspiration from autonomous control methodologies in leading-edge industries, the system predicts future behavior based on iterative calculations, dynamically adapting pump speed, fans speed and solenoid valves openings to converge rapidly on optimal operating points. It also adjusts performance based on external constraints such as noise limits, water availability, or energy costs — for example, consuming more energy to save water in water-stressed regions or balancing noise restrictions in urban deployments.

This unique, self-optimizing end-to-end control system maximizes energy efficiency, sustainability, and operational simplicity, extending pump life cycles and ensuring the most environmentally responsible data center cooling solution available today.

This vertically integrated, autonomous system — including smart racks, the advanced CDU, and the intelligent dry cooler — represents a world-first in end-to-end, intelligent, sustainable, communication-free, and data-driven data center cooling.

Why is this important?

This innovation is critical because it marks a decisive step toward radically more sustainable, efficient, and autonomous data center cooling — addressing the growing demands of digital infrastructure while reducing its environmental footprint.

By using fewer, smaller components, we are saving power, cutting transport costs and reducing carbon impact. Using fewer fans on the dry cooler means up to 50% lower energy consumption on the cooling cycle – and the new pad system means 30% lower water consumption in the cooling system. The system is fully autonomous, avoiding human error. A temperature gradient of 20K on the primary loop – four times higher than the industry average – means that flow rates can be lower and water efficiency is higher. The system doesn’t rely on Wi-Fi or cabling, and the predictive control constantly adapts to external conditions or situational goals, feeding into a data lake to help continuously optimize performance.

Today’s world is built on technology, and datacenters are a key part of that technology, but there is a pressing need to ensure we can maintain human progress without incurring a significant carbon footprint. Power and water efficiency is a key part of this equation in the datacenter industry, and our innovation in the Smart Datacenter continues our trajectory of supporting today’s needs without compromising the world of tomorrow.