WGU D446 OA COMPREHENSIVE EXAM
PREP QUESTIONS AND ANSWERS
1. In a Spine-Leaf network architecture, what is the primary purpose of the Leaf layer?
A. To connect directly to end-nodes like servers, storage arrays, and firewalls
B. To aggregate traffic from the spine switches and connect to the core
C. To provide high-speed routing between different data centers
D. To serve as the primary gateway for all North-South traffic only
Answer: A
Conceptual Explanation: In a Spine-Leaf topology, the leaf switches connect to all end-
devices (servers, storage). Every leaf switch is connected to every spine switch, providing
low-latency East-West traffic.
2. According to the Uptime Institute, which Tier level requires ‘Concurrent Maintainability’
for all site infrastructure components?
A. Tier I
B. Tier III
C. Tier II
D. Tier IV
,Answer: B
Conceptual Explanation: Tier III is defined by ‘Concurrent Maintainability,’ allowing any
component to be removed or replaced without impacting the IT load. Tier IV goes further
by being ‘Fault Tolerant.’
3. Calculate the Power Usage Effectiveness (PUE) if a data center consumes a total of 500 kW
of power, where 300 kW is used specifically by IT equipment.
A. 0.6
B. 2.0
C. 1.25
D. 1.67
Answer: D
Conceptual Explanation: PUE = Total Facility Power / IT Equipment Power. So,
= 1.666…, which rounds to 1.67.
4. Which type of UPS (Uninterruptible Power Supply) offers the highest level of protection by
constantly converting AC to DC and back to AC?
A. Standby UPS
B. Double-conversion Online UPS
C. Line-interactive UPS
D. Ferroresonant UPS
, Answer: B
Conceptual Explanation: Double-conversion (Online) UPS systems isolate the output from
the input, ensuring a clean sine wave and zero transfer time during a power failure.
5. What is the primary advantage of implementing a Hot Aisle Containment System (HACS)
compared to Cold Aisle Containment?
A. It eliminates the need for CRAC units entirely
B. It is significantly cheaper to install in existing legacy data centers
C. It allows for higher supply air temperatures without risking equipment overheating
D. It makes the rest of the room a comfortable working temperature for technicians
Answer: D
Conceptual Explanation: In HACS, the hot air is contained and vented, leaving the rest of
the room as a ‘cold’ reservoir, which is more comfortable for personnel and generally more
efficient for cooling returns.
6. Which fire suppression system is ‘dry’ until a fire is detected, requiring two independent
signals (e.g., heat and smoke) before water enters the pipes?
A. Wet pipe system
B. Deluge system
C. Pre-action system
D. Clean agent system
PREP QUESTIONS AND ANSWERS
1. In a Spine-Leaf network architecture, what is the primary purpose of the Leaf layer?
A. To connect directly to end-nodes like servers, storage arrays, and firewalls
B. To aggregate traffic from the spine switches and connect to the core
C. To provide high-speed routing between different data centers
D. To serve as the primary gateway for all North-South traffic only
Answer: A
Conceptual Explanation: In a Spine-Leaf topology, the leaf switches connect to all end-
devices (servers, storage). Every leaf switch is connected to every spine switch, providing
low-latency East-West traffic.
2. According to the Uptime Institute, which Tier level requires ‘Concurrent Maintainability’
for all site infrastructure components?
A. Tier I
B. Tier III
C. Tier II
D. Tier IV
,Answer: B
Conceptual Explanation: Tier III is defined by ‘Concurrent Maintainability,’ allowing any
component to be removed or replaced without impacting the IT load. Tier IV goes further
by being ‘Fault Tolerant.’
3. Calculate the Power Usage Effectiveness (PUE) if a data center consumes a total of 500 kW
of power, where 300 kW is used specifically by IT equipment.
A. 0.6
B. 2.0
C. 1.25
D. 1.67
Answer: D
Conceptual Explanation: PUE = Total Facility Power / IT Equipment Power. So,
= 1.666…, which rounds to 1.67.
4. Which type of UPS (Uninterruptible Power Supply) offers the highest level of protection by
constantly converting AC to DC and back to AC?
A. Standby UPS
B. Double-conversion Online UPS
C. Line-interactive UPS
D. Ferroresonant UPS
, Answer: B
Conceptual Explanation: Double-conversion (Online) UPS systems isolate the output from
the input, ensuring a clean sine wave and zero transfer time during a power failure.
5. What is the primary advantage of implementing a Hot Aisle Containment System (HACS)
compared to Cold Aisle Containment?
A. It eliminates the need for CRAC units entirely
B. It is significantly cheaper to install in existing legacy data centers
C. It allows for higher supply air temperatures without risking equipment overheating
D. It makes the rest of the room a comfortable working temperature for technicians
Answer: D
Conceptual Explanation: In HACS, the hot air is contained and vented, leaving the rest of
the room as a ‘cold’ reservoir, which is more comfortable for personnel and generally more
efficient for cooling returns.
6. Which fire suppression system is ‘dry’ until a fire is detected, requiring two independent
signals (e.g., heat and smoke) before water enters the pipes?
A. Wet pipe system
B. Deluge system
C. Pre-action system
D. Clean agent system
