Exin EPI Certified Data Centre Specialist CDCS Exam Questions

Answer : A

OM5 is optimized for Short Wavelength Division Multiplexing (SWDM) between 850--953 nm. This allows transmission of multiple wavelengths over a single fiber pair, reducing the number of fibers required for high-speed links.

OM4 already supports 100 GbE to 150 m, but OM5 with SWDM extends reach and reduces cabling bulk.

Option B is false because OM5 offers distinct SWDM benefits.

Option C is incorrect---OM5 is laser-optimized, not LED-based.

Option D is misleading; OM5 doesn't extend 100 GbE to 500 m (that requires single-mode OS2 fiber).

Thus, the key advantage is SWDM support.

Answer : A

For balanced three-phase systems: where .

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Answer : D

LCC (Life Cycle Cost) is the metric that accounts for capital cost, operational energy, maintenance, and disposal/replacement. This holistic view is critical when evaluating cooling technologies like CRACs, CRAHs, chilled water, or free cooling systems.

HER (Heat Exchange Ratio) and COP (Coefficient of Performance) measure operational efficiency but not total lifecycle costs.

PUE measures overall data center efficiency but not specifically cooling CAPEX/OPEX.

Thus, LCC is the comprehensive metric that covers installation, operation, and disposal.

Answer : C

Hydrogen sulfide (HS) is a corrosive gas that readily reacts with metals, especially copper and silver found in circuit boards, connectors, and power supply components. Even at concentrations below human detection thresholds, HS can cause sulfidation corrosion leading to intermittent connections, failure of solder joints, and increased failure rates of electronic equipment.

ASHRAE Technical Committee 9.9 has documented multiple failures in data centers due to corrosive gases (notably sulfur-bearing compounds). Therefore, high humidity combined with HS presence accelerates this risk.

HS does not affect static flooring properties (B) or fire suppression agent chemistry (D). Option A is clearly incorrect as the risk is well-documented.

Answer : A

PUE (Power Usage Effectiveness) is the most widely used metric to evaluate the energy efficiency of data centers. Defined by The Green Grid and adopted in ISO/IEC 30134-2, PUE is the ratio of the total facility power to the ICT (IT load) power.

Formula:

Total Facility Power includes all electrical consumption: IT, cooling, lighting, power distribution losses, UPS inefficiency, etc.

ICT Equipment Power is only the load drawn by servers, storage, and networking gear.

An ideal PUE is 1.0, meaning all power is used by ICT equipment with no overhead. Typical enterprise values are 1.5--2.0, while hyperscale operators target <1.2.

Other options are incorrect:

B represents the inverse metric, known as DCiE (Data Center infrastructure Efficiency).

C and D are partial subsystem efficiency metrics, not the global PUE.

Answer : B

The aisle pitch is the total width of a rack row plus cold aisle plus rack row. For 1.0 m racks on each side with cold aisle containment, ASHRAE and TIA-942 recommend the 7-tile rule (each tile ~0.6 m). This ensures enough width for equipment clearance, airflow distribution, and human access.

5-tile pitch is too narrow, restricting containment effectiveness.

8--10 tiles may be used in some hyperscale layouts but are not standard for 1 m racks.

Thus, the correct design recommendation is the 7 tiles pitch rule.

Answer : D

Relative Humidity (RH) is defined as the ratio of the actual water vapor content in the air to the maximum possible water vapor content at a given temperature. To calculate RH:

Dry bulb temperature (DBT): the ambient air temperature.

Wet bulb temperature (WBT): the temperature measured by a thermometer covered with a wet wick, influenced by evaporative cooling.

Using DBT and WBT, the humidity ratio and dew point can be determined with a psychrometric chart or Mollier diagram. From there, RH is calculated as:

Options A and B are incomplete, while option C is an experimental method, not standard practice. The recognized method is option D.