PUE: know to bring down

Published on October 12, 2018

PUE: know to bring down

    Data centers are the “factories” of the new Digital Economy. Functioning on their base of IT services play an increasingly important role in the activities of companies and organizations. In many cases, they become the basis of production and business processes. Therefore, the company's success in the market depends on reliable and efficient data center operation. And problems and interruptions in such work are fraught with serious financial losses.

    In addition to reliability, a key feature of modern data centers is energy efficiency. This indicator is receiving more and more attention. Not surprisingly, by the end of 2017, the total power consumption of all data centers in the world turned out to be comparable with the power consumption of Russia. And this is about 800 TWh. The data center industry is constantly evolving, they consume more and more energy. The estimated annual increase in data center capacity in the world is 8-12%. In Russia, the situation is similar.

    The use of green technologies allows not only to save on electricity, but also to reduce the cost of engineering equipment necessary for the operation of the data center. The lower the level of electricity consumed by the data center, the less it will be necessary to pay for uninterruptible power supplies, air conditioning systems and other elements of the engineering infrastructure.

    To assess the energy efficiency of the data center, the PUE (Power Utilization Efficiency) indicator proposed by the Green Grid organization is used. It is defined as the ratio of the total electrical energy consumed by the data center to the energy consumed directly by IT equipment. Let's give an example. If the data center receives a power of 2 MW from the power grid, and only 1 MW reaches the IT equipment, then the PUE of this object will be 2. If you can reduce the “overhead” and bring the 1.5 MW to the IT equipment, PUE will drop to 1.33 (2 / 1.5 = 1.33). The smaller the PUE value, the more efficiently the power is used.

    According to the organization Uptime Institute, in 2007, the average PUE data center was at 2.5. In 2018, this figure fell to a value of 1.58. Moreover, there are data centers in which PUE is at the level of 1.1 and even lower. Ideal when PUE = 1. But in practice it is unattainable, since the efficiency of engineering equipment, for example, UPS, cannot be equal to 100%.

    There are various ways to improve energy efficiency (lower PUE). One of the most energy-intensive systems of modern data centers is the cooling system. The use of technologies of natural cooling (free cooling) can significantly reduce energy consumption for cooling. The essence of free cooling is the use of cool outside air for cooling. This air can be supplied through the filter system directly to the server rooms (direct free cooling) or, passing through heat exchangers, cool the air circulating inside the data center (indirect free cooling). It is clear that reducing PUE contributes to the use of UPS with higher efficiency, as well as reducing losses in the transmission of electricity - when the energy through cables or busbars goes to IT equipment.

    In order to increase energy efficiency, it is not necessary to spend large amounts of money on the purchase of new equipment with higher efficiency. There are many recipes for the modernization of already operated facilities with a minimum investment. For example, you can close the slots in cabinets to eliminate cold air leaks, isolate hot or cold corridors, optimize the placement of servers in cabinets, for example, by moving a high-loaded server to a “cooler” rack, etc.

    But in order to carry out such work it is necessary, first of all, to have information about current energy consumption. The total consumption of the data center (the numerator in the calculation of the PUE coefficient) is not difficult to measure - for this it is sufficient to install the appropriate measuring devices on the electrical switchboard inputs. But in order to get the denominator, it is necessary to measure energy consumption directly at the IT equipment connection points, i.e. in racks. This requires the installation of distribution PDUs with means of controlling energy consumption (such PDUs are also called intelligent). Consider the capabilities of these devices on the example of the equipment of the British company PDU eXpert.

    The PDU eXpert company develops and manufactures a wide range of PDU products: from simple non-intelligent units with different numbers of different types of sockets to intelligent units of the KWX line.

    KWX-N family units are available in four versions:

    • N1 models provide total power control through the entire PDU, including the total current (A), the input and output voltage (V), and the total electricity consumption (kWh) by all devices connected to the PDU;
    • N2 models differ from N1 models in that they allow monitoring at the level of each individual outlet. They make it possible to obtain data on the power consumption of individual devices connected to the PDU;
    • The N3 devices have all the same features as the N1 models, but additionally allow the user to remotely turn on and off individual outlets. This may be convenient for servicing IT complexes, for example, when you need to restart a server remotely;
    • Finally, the most functional N4 models provide the ability to monitor individual outlets (like N2) and remotely enable / disable them (like N3). They are in demand in cases where the requirements for monitoring and remote maintenance are maximum.



    The KWX family also includes "advanced" devices with AVR functions. The KWX-ATS (Automatic Transfer Switch) series devices, in addition to the capabilities of the intelligent PDU, are endowed with the functionality of automatic reserve transfer (ATS) and sequential equipment switching (sequential startup). They provide automatic switching between the main and backup power sources without interrupting the supply of electricity to the load. In the case when the main source of power supply becomes unavailable, KWX-ATS will transfer the load to the backup source, and the switching occurs within 8 ms. The device can operate at temperatures up to + 55 ° C, which allows it to be placed in the hot corridor of the server rooms.


    In addition, the eXperts KWX-ATS PDU product line has an integrated environmental monitoring feature. The sensors connected to the device can be connected in a chain - up to eight sensors. These may include temperature, humidity, smoke detectors, or the presence of water. To increase the level of security can be used sensors door shutter and infrared radiation. Environmental monitoring is provided from a user-friendly software control interface, which also allows you to enter user accounts, set thresholds, and set alarms.

    Software control KWX-ATS has a convenient interface that provides easy access to the control of the main device, as well as its subordinate AVR-PDU (up to three devices in the chain). Through this interface, you can both monitor current power consumption and set limit values. In case of exceeding the limit values, the visual and sound signals are automatically switched on. Warning messages can be sent via SMS-messages or by e-mail to certain users.



    By combining the functions of an intelligent PDU, automatic backup system, environmental monitoring and access control, the KWX-ATS can be the ideal solution for a small data center. And the presence of the powerful Symbiosis control system in the eXpert PDU product portfolio makes them an effective tool for large data centers and even a complex of several data centers. By the way, Symbiosis software supports both PDU eXpert devices and PDUs from Raritan, APC (Schneider Electric), Eaton and other companies, various air conditioners and sensors.

    Let us consider with an example how the use of KWX-ATS devices helps to increase the energy efficiency of the data center, while avoiding the additional costs of upgrading it. Suppose you need to install several new servers in a running data center. The availability of information on the current energy consumption of the equipment already installed will make it possible to determine in which cabinets there is an energy reserve for connecting new equipment. Using the functions of monitoring the working environment will give the opportunity to see where the temperature is the lowest, which means that there are enough resources for cooling additional equipment. By comparing this data, you can choose the optimal place where you can install new servers without upgrading the existing cooling and power supply systems. It turns out that you add IT load without increasing the power of the cooling system, which,

    But it's not just energy optimization. In the absence of information about the current energy consumption, you can make an erroneous decision on choosing a rack for hosting servers. This solution may simply be based on data on available space in the rack. But if high-loaded servers are installed in the rack, it is possible that adding another device will result in exceeding the permissible limit, which is fraught with disabling this rack from the power supply system.

    In the case of using KWX-ATS, such a negative scenario is practically excluded. These devices allow the most efficient use of such expensive resources for any data center, such as electricity, cold air and physical space in racks. In addition, AVR functions will ensure reliable switching of IT equipment to a backup source. So KWX-ATS is not only efficiency, but also high reliability.

    This is well understood and appreciated by leading companies around the world who actively use KWX-ATS equipment. In particular, these technical solutions were installed in their IT complexes by the Aramco oil company from Saudi Arabia. The commercial data center service provider Hostdime has equipped all its facilities with such devices in Brazil, the UK and the USA.

    Among the reasons for using KWS-ATS, customers focus on ensuring the uninterrupted operation of IT equipment - as already mentioned, switching from the main power supply to the backup power supply takes 8 ms without pain for the equipment - as well as an excellent balance of
    price and quality. For example, the KWX-ATS32A1H1 model has one output 32A, to which a 48-socket basic PDU is connected - this bundle provides significant cost savings.