Liquid-cooled data centers: Five core breakthroughs from cooling revolution to the future of computing power

Efficient cooling, stable protection

In traditional air-cooled data centers, air as a refrigerant has many limitations when transferring heat. Liquid-cooled data centers have achieved a major breakthrough. They use liquid as a refrigerant, which has brought a qualitative leap in server heat dissipation. The thermal conductivity of liquid is about 25 times that of air. This feature enables the liquid cooling system to conduct the heat generated by the server more quickly.

From the principle of heat transfer, the molecular distance between liquids is smaller and the intermolecular force is stronger. Therefore, when absorbing heat, it can more efficiently transfer heat energy to the surrounding molecules, thereby achieving rapid heat dissipation. When key components such as the CPU in the server generate a lot of heat, the coolant in the liquid cooling system can quickly contact it and take away the heat, ensuring that the CPU always works within a suitable temperature range.

Taking the data center of a large Internet company as an example, when air cooling is used for heat dissipation, the CPU temperature often soars to more than 80°C when the server is running under high load, which not only seriously affects the performance of the server, but also shortens the service life of the hardware. After replacing the server with liquid cooling, the CPU temperature can be stably controlled at around 60°C even when running at full load for a long time. This comparison fully demonstrates the excellent ability of liquid cooling technology in stabilizing CPU temperature, providing a solid guarantee for the efficient and stable operation of the server.

In actual applications, liquid cooling technology can also effectively cope with the heat dissipation challenges of sudden server operations. When the server encounters sudden high-load tasks and the operating power surges, the liquid cooling system can quickly remove the extra heat generated with its efficient heat dissipation capacity, avoid a sharp increase in the internal temperature of the CPU, and ensure that the CPU can be overclocked within a certain range without overheating failure. This enables the server to maintain stable performance when facing complex and changeable workloads, providing reliable support for business continuity.

Energy saving and noise reduction

In the operating costs of data centers, energy consumption accounts for a considerable proportion, and the energy consumption of the cooling system is a key part of it. The cooling system of traditional air-cooled data centers relies on a large number of air-conditioning equipment and fans, which consume a lot of electricity during operation. According to statistics, the energy consumption of the cooling system of traditional air-cooled data centers usually accounts for 30% - 40% of the total energy consumption, which makes the energy utilization efficiency (PUE) of the data center higher, generally between 1.4 - 2.0.

Liquid-cooled data centers show great advantages in energy saving. Since the liquid cooling system uses liquid to directly contact the heat-generating components to dissipate heat, its heat dissipation efficiency is higher, and it does not need to rely on a large number of mechanical refrigeration equipment and fans like air-cooled systems. This greatly reduces the energy consumption of liquid-cooled data centers, and the PUE value can be easily reduced to between 1.1 and 1.2. Some high-efficiency liquid cooling systems can even reduce the PUE value to below 1.05. This means that for data centers using liquid cooling technology, for every unit of energy consumed, more of it is used for the operation of IT equipment rather than wasted in the cooling process, thereby greatly improving energy efficiency.

Take a data center with a power of 10MW as an example. If traditional air cooling technology is used, the total power consumption is 15MW according to the PUE value of 1.5, of which 5MW is used for non-IT equipment such as refrigeration. After adopting liquid cooling technology, assuming that the PUE value drops to 1.1, the total power consumption becomes 11MW, and the power consumption of non-IT equipment is only 1MW. In contrast, liquid-cooled data centers can save a lot of electricity every year, which not only reduces operating costs, but also reduces the pressure of energy consumption on the environment, which is in line with the current concept of green development.

In addition to energy saving, liquid-cooled data centers also perform well in noise reduction. The air conditioning system and fan of traditional air-cooled data centers will generate a lot of noise during operation, which will not only interfere with the staff inside the data center, but also may affect the surrounding environment. In the liquid cooling system, the main operating component is the circulation pump, which has relatively low operating noise. Under the same heat dissipation conditions, the noise generated by the liquid cooling system is usually 10-20 decibels lower than that of the traditional air cooling system, which can create a quieter operating environment for the data center and achieve the effect of a "silent computer room".

Space expansion, computing power soaring

In the development process of data centers, increasing the server density within a unit space to obtain higher computing efficiency has always been an important goal pursued by the industry. The emergence of liquid cooling technology provides strong support for the realization of this goal.

Liquid-cooled data centers have unique advantages in space utilization. Unlike traditional air-cooled data centers, although liquid-cooled data centers have added pumps and coolant systems, they save huge air-conditioning systems and corresponding air-cooling infrastructure. These saved spaces provide more possibilities for server deployment. Taking a standard 2,000 square meter data center as an example, the actual area available for placing servers in traditional air-cooled data centers is about 1,200 square meters because of the need to reserve space for air-conditioning systems, ventilation ducts, etc. After adopting liquid cooling technology, the space occupied by facilities such as air conditioning systems is removed, and the area available for server deployment can be increased to about 1,600 square meters, greatly improving space utilization.

Not only that, the excellent cooling capacity of liquid cooling technology makes it sufficient to cope with the cooling work of high-power density data centers. This means that in liquid-cooled data centers, higher density servers can be configured. Traditional air-cooled data centers are limited by heat dissipation capacity, and the power density of a single cabinet can usually only reach 10-15kW, while the power density of a single cabinet in a liquid-cooled data center can be easily increased to 50-100kW, and even in some advanced liquid cooling technology applications, the power density of a single cabinet can exceed 150kW. In the same space, liquid-cooled data centers can accommodate more servers, and these servers can run stably at higher power, thereby greatly improving the computing efficiency of data centers.

With the rapid development of emerging technologies such as artificial intelligence and big data analysis, the demand for computing power in data centers has exploded. High-power density data centers have become the key to meeting these needs, and liquid cooling technology, as the core supporting technology for achieving high-power density data centers, is of great importance. In the field of artificial intelligence training, NVIDIA's GB200 series requires direct liquid cooling of the chip, with a rack power density of up to 130kW. Under such high power density requirements, only liquid cooling technology can ensure that the chip maintains a stable temperature while running efficiently, thereby achieving excellent computing performance. If traditional air cooling technology is used, it will not be able to meet the heat dissipation requirements of such high power density. The server is likely to frequently fail due to overheating, seriously affecting computing efficiency and the normal development of business.

Fearless of the environment, stable as always

In the huge system of data centers, environmental factors have a vital impact on their operating efficiency and stability, and altitude is a key factor that is often overlooked but has far-reaching impact.

For traditional air-cooled data centers, the impact of changes in altitude cannot be underestimated. As the altitude increases, the atmospheric pressure gradually decreases, and the air density also decreases. When the cooling effect of the air medium decreases, the air heat dissipation capacity of the air-cooled data center will drop significantly. According to relevant research, when the altitude reaches about 4,000 meters, the air density is only 60% of the original density, which will cause the heat dissipation efficiency of the air-cooled server to decrease by about 40%. In this case, in order to ensure the heat dissipation efficiency of the data center and maintain the normal operating temperature of the server, the air-cooled data center has to lower the temperature of the air conditioning system. This move will undoubtedly consume more energy, not only increase operating costs, but also may cause local hot spots in the chip due to insufficient heat dissipation efficiency, which will cause the server chip to downclock or even shut down, seriously affecting the normal operation of the data center and greatly increasing the risk of business interruption.

However, liquid-cooled data centers have shown strong environmental adaptability. The specific heat capacity of liquid is not affected by altitude and air pressure, which enables liquid-cooled data centers to maintain excellent heat dissipation efficiency in high-altitude areas. Whether the data center is located in a low-altitude plain area or a high-altitude mountainous area, the liquid cooling system can stably remove the heat generated by the server to ensure that the operating efficiency and performance of the data center are not affected. In the western cluster hub area of the "East Data West Computing" project, some data centers are located in a high-altitude environment. The application of liquid cooling technology effectively solves the heat dissipation problem, ensures the efficient and stable operation of the data center, enables data to be quickly processed and stored in the western region, and promotes the coordinated development of computing power in the east and west.

The characteristics of liquid-cooled data centers that are not restricted by the geographical environment are also reflected in their adaptability to different climatic conditions. Whether it is a hot desert area or a cold polar area, the liquid cooling system can work normally. In hot desert areas, the air conditioning system of traditional air-cooled data centers needs to run at full capacity to combat high temperature environments, which not only consumes a lot of energy, but may also cause poor heat dissipation due to excessively high ambient temperatures. Liquid-cooled data centers, with their efficient heat dissipation capabilities, can easily cope with high temperature challenges and ensure that servers can still operate stably in harsh environments. In the cold polar regions, although the low temperature environment seems to be conducive to heat dissipation, the equipment in the air-cooled data center may malfunction due to the low temperature, such as fan jamming, lubricant solidification and other problems. Liquid-cooled data centers do not have these problems. The physical properties of the coolant are stable, and the heat dissipation performance will not be affected by low temperature, which makes it possible to deploy data centers in polar regions.

Reduce failures and extend life

As the power density of data centers continues to rise, traditional air-cooled heat dissipation technology has gradually exposed its inefficiency in dealing with the growing heat. When the server is in a high-load operation state for a long time, the traditional air-cooled heat dissipation system is difficult to discharge the generated heat in time, which makes the temperature inside the server continue to rise, and then leads to a significant increase in the server failure rate. According to relevant research, when the internal temperature of the server increases by 10℃, its failure rate will increase by about 50%. In traditional air-cooled data centers, server failures caused by poor heat dissipation are common, which will not only cause serious consequences such as data loss and business interruption, but also increase the operation and maintenance costs and repair time of the data center.

Liquid cooling technology, with its efficient heat dissipation capacity, provides an effective way to solve this problem. The liquid cooling system can quickly remove the heat generated by the server, ensuring that the server always runs in a low-temperature and stable environment. This greatly reduces the risk of hardware failure caused by poor heat dissipation and extends the service life of the server. Take the data center of a financial institution as an example. Before the liquid cooling technology was adopted, the data center had more than 50 failures due to server overheating each year. Each failure took hours or even days to repair, which not only affected the normal business development, but also brought huge economic losses. After the liquid cooling technology was adopted, the operating temperature of the server was effectively controlled, and the number of failures was reduced to less than 5 times a year, greatly improving the stability and reliability of the data center.

From the hardware level, liquid cooling technology has a significant protective effect on server hardware. In the traditional air-cooled environment, high temperature will accelerate the aging and wear of the internal hardware of the server. For example, in a high-temperature environment, the internal electronic migration of the CPU will be aggravated, resulting in a shortened CPU life; the probability of data errors in memory chips will also increase due to high temperature. Liquid cooling technology can reduce the operating temperature of the hardware, slow down the speed of these physical and chemical changes, and thus extend the service life of the hardware. The server's hard disk has more stable read and write performance and lower failure rate in a low temperature environment. This enables the server to maintain higher performance and reliability during long-term operation, reduces system downtime caused by hardware failure, and provides a solid guarantee for the stable operation of the data center.