The expected time to Recover/Repair from a system from a failure is defined as.
Correct Answer: D
The expected time to recover or repair from a system from a failure is defined as MTTR (mean time to recovery or mean time to repair). MTTR is the average time it takes to restore a system or product to its normal operation after a failure. MTTR includes the time spent on detecting, diagnosing, and fixing the problem. MTTR is an important metric for measuring the reliability and availability of a system or product, as well as the efficiency and effectiveness of the incident management process. A lower MTTR indicates a faster and more reliable recovery or repair process. References: *EPI Data Centre Professional (CDCP®) Preparation Guide, page 17 *What is MTTR? | IBM *Explained: All Meanings of MTTR and Other Incident Metrics
Question 7
An optical fiber cable comes with the specifications 50/125 um. What do the numbers represent?
Correct Answer: B
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 (m), which are one millionth of a meter. For example, a 50/125 m cable has a core diameter of 50 m and a cladding diameter of 125 m. The coating diameter is usually 250 m, but it is not part of the specifications. References: Multimode Optical Fiber Selection & Specification - Corning, Optical Fiber OM3 (50/125µm Multimode Fiber), 50/125 Graded-Index OM2 Optical Fiber - OFS
Question 8
When having two non-synchronized power sources, the ATS / STS need to be of the type:
Correct Answer: A
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. References: 1: CDCP Preparation Guide, page 17, section 2.3.1 2: STS in data centres - Borri3, page 1, section 1 4: Using Static Transfer Switches to Enhance Data Center ... - Donwil5, page 1, section 1 6: What is an Automatic Transfer Switch (Power)? | Ethan Banks7, page 1, section 1
Question 9
What is a requirement for both CCTV cameras and recording equipment?
Correct Answer: C
A UPS (Uninterruptible Power Supply) is a device that provides backup power to electrical equipment in case of a power outage or fluctuation. A UPS is essential for both CCTV cameras and recording equipment, as it ensures that the surveillance system can continue to operate and record without interruption or data loss. A UPS can also protect the CCTV cameras and recording equipment from damage caused by power surges or spikes. Connecting both CCTV cameras and recording equipment to a UPS is a requirement for data centres, as it enhances the security and reliability of the surveillance system. References: Technical Specification - GeM, [What is a UPS? | Uninterruptible Power Supply | APC by Schneider Electric], [Why You Need a UPS for Your CCTV System - CCTV Camera World].
Question 10
Sprinkler heads used in computer rooms activate at what temperature?
Correct Answer: A
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. References: 1: CDCP Preparation Guide, page 24, section 2.4.3 2: Sprinkler Systems in Data Centers3, page 1, section 1 4: Data Center Fire Protection5, page 1, section 2 6: Data Center Sprinkler System Design7, page 1, section 1
