Exin CDCP - Certified Data Centre Professional (CDCP)

Availability and reliability are two important aspects of data centre performance that measure how often the system is operational and how dependable it is. According to the EPI Data Centre Framework, availability is the percentage of time that a system or component is in an operable state, while reliability is the probability that a system or component will perform its required function under given conditions for a specified period of time. Both availability and reliability can be affected by various factors, such as design, maintenance, human error, power supply, security, etc. One of the factors that can have a significant impact on both availability and reliability is cooling. Cooling is essential for maintaining the optimal temperature and humidity levels for the IT equipment and preventing overheating, which can cause failures, downtime, and reduced lifespan. Inadequate cooling can result from insufficient capacity, poor airflow management, faulty components, or environmental conditions. Inadequate cooling can reduce the availability and reliability of the data centre by increasing the risk of thermal stress, hot spots, performance degradation, and equipment damage. Therefore, cooling is a critical factor that can affect availability and reliability in a data centre.

According to the CDCP Preparation Guide1, risk can be defined as the product of impact and probability. Impact is the measure of the negative consequences or losses that may result from a risk event, such as downtime, data loss, or damage to the data centre. Probability is the measure of the likelihood or frequency of a risk event occurring, based on historical data, expert judgment, or statistical analysis. By multiplying impact and probability, risk can be quantified and compared, which helps in prioritizing and mitigating the risks. For example, a risk event that has a high impact but a low probability may have the same risk level as a risk event that has a low impact but a high probability.

Cooling capacity is the measure of a cooling system’s ability to remove heat from a space. The most preferred unit of measure for cooling capacity is watt (W), which is the SI unit for power. Watt is defined as the amount of energy transferred or converted per unit time. One watt is equal to one joule of energy per second. Using watt as the unit of measure for cooling capacity allows for easy comparison and calculation of the cooling performance and efficiency of different cooling systems.

Other units of measure for cooling capacity are ton, BTU, and horsepower, but they are less common and less convenient than watt. Ton is a unit of measure that describes how much water at freezing temperature can be frozen in 24 hours, equivalent to 3.5 kW or 12,000 BTU/h. BTU (British Thermal Unit) is a unit of measure that describes the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit, equivalent to 0.293 W. Horsepower is a unit of measure that describes the rate at which work is done, equivalent to 746 W.

Infrared humidifiers are a type of humidifier that use quartz lamps to heat water in an open pool and evaporate it into the air. They are energy-intensive and require frequent maintenance and cleaning. They are not recommended for data centers, as they can introduce contaminants and bacteria into the air, and increase the risk of fire and electrical hazards.

Patch cables of a lower class than the structured cabling can degrade the overall link performance, so it is best practice to use the same or higher class.

The current recommended temperature for ICT equipment as described in the ASHRAE TC 9.9 guideline is 18-27 C (64.4 - 80.6°F). This is the recommended range for the dry-bulb temperature at the inlet of the servers, which is the most critical parameter for ensuring the optimal performance and reliability of the ICT equipment. The recommended range is based on the thermal specifications of the majority of the ICT equipment in the market, as well as the energy efficiency and environmental considerations of the data centre cooling systems. The recommended range is suitable for Classes A1 to A4 of the ASHRAE thermal guideline classes, which cover different types and generations of ICT equipment.

A design consideration that should be implemented with an Inergen-based fire suppression system is to install pressure relief valves in the room that needs protection. Inergen is a clean agent fire suppression system that uses a mixture of inert gases (nitrogen, argon, and carbon dioxide) to displace the oxygen in the room and extinguish the fire. However, when Inergen is released into the room, it creates a sudden increase in pressure, which can damage the walls, doors, windows, and ceilings of the room. To prevent this, pressure relief valves are required to vent the excess pressure to the outside and maintain a safe pressure level inside the room. Pressure relief valves should be designed and installed in accordance with the relevant standards and codes, such as NFPA 2001 and ISO 14520.

The primary reason to install a monitoring system in the data centre is to notice abnormalities early so that actions can be taken to avoid disasters, according to the CDCP Preparation Guide1 and various web sources234. A monitoring system is a system that collects and analyzes data about the power, cooling, environmental, and security conditions in the data centre, and alerts the operators or managers about any issues or threats that may affect the performance, availability, or reliability of the data centre. A monitoring system can help to prevent or minimize the impact of disasters, such as power outages, fire, water damage, overheating, equipment failure, or cyberattacks, by providing timely and accurate information that enables fast and corrective action. A monitoring system can also help to improve the energy efficiency, capacity planning, and asset management of the data centre, by providing useful insights and trends that support informed decision making.

The casters and feet under the rack are used to support the weight of the rack and its equipment, and to allow the rack to be moved if needed. However, the casters and feet should also be designed to avoid putting too much pressure on the floor tile, especially if the data centre uses a raised floor system. A too heavy point load on the floor tile can cause the tile to crack, deform, or collapse, which can damage the rack, the equipment, and the underlying infrastructure. To prevent this, the casters and feet should be larger, so that they can distribute the weight over a larger area and reduce the point load. The casters and feet should also be compatible with the floor type and the load rating of the floor tile.

When having two non-synchronized power sources, the ATS / STS need to be of the type break before make, which means that the switch disconnects from one source before connecting to the other source. This prevents any short circuit, back feed, or phase mismatch that could occur if the two sources were connected simultaneously. Break before make switches are also known as open transition switches, because they create a brief interruption in the power supply during the switching process. This interruption is usually acceptable for most ICT equipment, as they have internal power supplies or batteries that can handle the transient. However, if the interruption is not acceptable, then the two power sources need to be synchronized before switching, which requires a make before break switch, also known as a closed transition switch. Make before break switches connect to the second source before disconnecting from the first source, which ensures a seamless transfer of power without any interruption. However, make before break switches require that the two sources have the same voltage, frequency, and phase, which can be achieved by using a synchronization module or a phase-locked loop.