CDCP Questions and Answers

The objective of data center fire protection is to suppress or extinguish a fire before it can cause significant damage to the equipment, personnel, or business continuity. Fire suppression systems are designed to reduce the heat, oxygen, or fuel elements of the fire triangle, and to limit the spread of fire and smoke. Fire suppression systems can be classified into two types: water-based and gas-based. Water-based systems include sprinklers, mist, and water spray systems, which use water as the extinguishing agent. Gas-based systems include inert gas, halocarbon, and clean agent systems, which use gases or chemicals as the extinguishing agent. The choice of fire suppression system depends on several factors, such as the fire risk, the type of fuel, the environmental impact, the reliability, the cost, and the compatibility with the data center equipment and operations.

MTBF stands for Mean Time Between Failures, and it is the arithmetic mean of time between the failing and the subsequent running of the system in a particular time period. MTBF is a measure of reliability that indicates how often a system or component fails during its operation. MTBF can be calculated by dividing the total operating time by the number of failures over a given period. For example, if a system operates for 1000 hours and experiences 5 failures, the MTBF is 1000/5 = 200 hours.

The requirement of Concurrently Maintainability becomes relevant starting from Rated-3, according to the Uptime Institute Tier Classification System1. Concurrently Maintainability means that any component or system in the data centre can be maintained or replaced without affecting the availability of the IT equipment. This requires having redundant capacity components and multiple independent distribution paths serving the IT equipment. Rated-3 data centres are designed to achieve Concurrently Maintainability and have a minimum uptime of 99.982%. Rated-4 data centres also have Concurrently Maintainability, but they also have Fault Tolerance, which means that they can withstand any single unplanned event without affecting the availability of the IT equipment. Rated-4 data centres have a minimum uptime of 99.995%. Rated-1 and Rated-2 data centres do not have Concurrently Maintainability, as they have only one distribution path serving the IT equipment and no redundant capacity components. Rated-1 data centres have a minimum uptime of 99.671% and Rated-2 data centres have a minimum uptime of 99.741%.

According to the CDCP® Preparation Guide, Class A fires involve ordinary combustible materials such as paper, wood and cloth. These materials leave behind ash or embers when they burn. Class A fires can be extinguished by water or other cooling agents that reduce the temperature of the fuel below its ignition point.

Optical fiber cables are composed of a core, a cladding, and a coating. The core is the central part of the fiber that carries the light signal. The cladding is the layer surrounding the core that reflects the light back into the core and prevents signal loss. The coating is the protective layer that covers the cladding and provides mechanical strength and environmental protection. The specifications of an optical fiber cable indicate the dimensions of the core and the cladding in microns (μm), which are one millionth of a meter. For example, a 50/125 μm cable has a core diameter of 50 μm and a cladding diameter of 125 μm. The coating diameter is usually 250 μm, but it is not part of the specifications.

According to the CDCP Preparation Guide1, magnetic fields of the type ‘H’ or ‘B’ are created when an electric current flows through a conductor, such as a wire or a coil. The magnetic field strength ‘H’ is proportional to the current ‘I’ and the number of turns ‘N’ of the coil, and inversely proportional to the length ‘l’ of the coil. The magnetic flux density ‘B’ is proportional to the magnetic field strength ‘H’ and the permeability ‘μ’ of the medium in which the magnetic field exists. The greater the current, the stronger the magnetic field and the magnetic flux density. The relationship between ‘H’, ‘B’, ‘I’, ‘N’, ‘l’, and ‘μ’ can be expressed by the following equations:

H = N I / l

B = μ H

Data centres are essential for supporting the IT operations and applications of various businesses across different industries. Data centre downtime can have a negative impact on the business results, such as loss of revenue, customer satisfaction, productivity, reputation, and competitive advantage. According to a web search, the average cost of data centre downtime in 2020 was $8,851 per minute, and the average duration of a data centre outage was 95 minutes1. This means that a typical data centre outage could cost a business over $840,000 in direct and indirect losses1. Therefore, data centre downtime can have a significant impact on the business results, regardless of the industry or sector.

A service corridor is a dedicated space within or adjacent to a data centre that allows access to the supporting facilities, such as power, cooling, fire suppression, security, and cabling systems, without interfering with the computer room operations. A service corridor helps to isolate the noise, vibration, heat, and dust generated by the supporting facilities from the sensitive equipment in the computer room. A service corridor also enhances the safety and efficiency of the maintenance and monitoring activities, as well as the flexibility and scalability of the data centre design.

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.

The fire triangle is a simple model that illustrates the three elements that a fire needs to ignite and sustain: oxygen, heat, and fuel. Oxygen is the oxidizing agent that enables the combustion reaction, heat is the energy source that raises the temperature of the fuel to its ignition point, and fuel is the material that reacts with oxygen and releases heat and light. Removing any one of these elements can extinguish a fire. For example, water can reduce the heat and the oxygen, sand or soil can smother the fuel and the oxygen, and fire extinguishers can displace the oxygen or lower the temperature.

The main difference between an Environmental Monitoring System (EMS) and a Building Management System (BMS) is that an EMS monitors only, while a BMS monitors and controls. An EMS is a system that collects and records data from various sensors and devices that measure environmental parameters, such as temperature, humidity, air quality, power, and water. An EMS provides alerts and reports based on the data, but it does not control or adjust the environmental conditions. A BMS is a system that integrates and manages various building systems, such as HVAC, lighting, security, fire, and access. A BMS not only monitors the data from these systems, but also controls and optimizes them to achieve the desired performance and efficiency. A BMS can also communicate with an EMS to receive data and provide feedback.

According to the EPI Data Centre Professional (CDCP®) Reference Materials, a core objective of a Business Value in an organization is to create value for customers and stakeholders1. This means delivering products or services that meet or exceed customer expectations, while also generating profits or benefits for the organization and its shareholders. Reducing costs, reducing the deficit, and increasing sales are possible ways to achieve this objective, but they are not the core objective itself.

According to the Certified Data Centre Professional (CDCP®) Reference Materials, the height of 1 "U" (rack unit) or "RU" (rack unit) is standardized at 1.75 inches, which is equivalent to 44.45 millimeters or 4.445 centimeters. This unit of measurement is globally used to define the internal mounting space in IT and telecommunications racks. Equipment manufacturers specify their devices’ height based on how many “U” the device occupies (for example, a 2U server is 3.5 inches high). The standardization ensures interoperability and planning efficiency within the data center environment.

The "U" (rack unit) system is essential for ensuring that racks and equipment from different manufacturers will fit together properly, facilitating modularity, expansion, and maintenance. The 1.75-inch specification is defined by several industry standards including EIA-310 and is referenced directly in the EPI CDCP training and its official exam preparation guides.

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.

Busbar trunking systems are a method of power distribution using rigid copper or aluminium conductors to distribute the power around a building. Busbar trunking systems have many advantages over cables, such as lower space requirements, higher short-circuit strength, lower fire load, and easier installation. One of the main advantages of busbar trunking is that it allows for flexibility in terms of power transmission and distribution. Busbar trunking systems can be easily relocated, modified, or expanded to accommodate changes in the building layout or load demand. Busbar trunking systems can also be fitted with various components, such as tap-off units, elbows, tees, and end feed units, to provide power to different locations and consumers. Busbar trunking systems can also be installed both overhead and under the raised floor, depending on the design and preference of the building.

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.

Sprinkler heads used in computer rooms activate at 57 °C (135 °F), which is the standard temperature rating for ordinary sprinklers. This is the temperature at which the heat-sensitive element of the sprinkler head, such as a glass bulb or a fusible link, breaks or melts, allowing water to flow from the sprinkler. Sprinkler heads are designed to activate only when exposed to a fire, not to ambient temperature fluctuations. Therefore, sprinkler heads should be installed at a sufficient distance from the heat sources, such as servers, racks, or ducts, to avoid accidental activation. Sprinkler heads should also be selected and installed in accordance with the relevant standards and codes, such as NFPA 13 and NFPA 75.

A fire extinguisher in the data centre that is classed as ABC is not suitable, because it contains dry chemical powder that can damage the ICT equipment and the data. ABC fire extinguishers are designed to fight Class A, B, and C fires, which are fueled by combustible materials, flammable liquids or gases, and electrical equipment, respectively. However, the dry chemical powder can leave a corrosive residue on the ICT equipment, which can cause short circuits, data loss, or malfunction. Moreover, the dry chemical powder can be difficult to clean, especially from the small spaces and crevices of the ICT equipment. Therefore, ABC fire extinguishers are not recommended for data centres, and should be replaced with more suitable fire extinguishers, such as clean agent fire extinguishers, which use gas or liquid that does not leave any residue or harm the ICT equipment.