CDCP Capacity Planning and Power Budgeting

Question 1

What is the formula for Power Usage Effectiveness (PUE), the primary metric for data center energy efficiency?

Accepted Answer

PUE = Total Facility Power / IT Equipment Power

Answer

PUE = Total Facility Power ÷ IT Equipment Power. A perfect PUE of 1.0 would mean all power goes directly to IT equipment with zero overhead. Typical modern data centers target below 1.5; hyperscalers often achieve 1.1–1.2. Values above 2.0 indicate significant inefficiency in cooling and power distribution.

Question 2

In data center capacity planning, what is 'stranded power'?

Accepted Answer

Allocated power capacity that cannot be used because cooling or space constraints are reached first

Answer

Stranded power occurs when power capacity has been allocated (reserved) but cannot actually be deployed because another constraint — typically cooling capacity or physical floor space — has been reached first. It represents wasted capital investment and is a key problem that DCIM tools and capacity planning aim to prevent.

Question 3

A data center operator wants to increase average rack density from 5 kW to 10 kW per rack. Which infrastructure element most commonly becomes the first bottleneck?

Accepted Answer

Cooling — removing heat from high-density racks exceeds conventional CRAC unit capacity

Answer

Cooling is the most common bottleneck when rack density increases. Traditional CRAC/CRAH units, raised-floor airflow, and hot/cold aisle containment are designed for lower densities. High-density racks (above ~10 kW) typically require targeted solutions such as in-row cooling, rear-door heat exchangers, or liquid cooling to remove heat effectively.

Question 4

What does 'white space' refer to in data center capacity planning terminology?

Accepted Answer

The portion of the computer room floor available for IT equipment deployment

Answer

White space is the customer-facing, revenue-generating floor area of a data center used for IT equipment — as opposed to 'gray space' (mechanical and electrical support areas) or 'white space on paper' (future buildout). Capacity planners track white space utilization to forecast when additional floor space will be needed.

Question 5

A data center is planning to add 200 new servers consuming an average of 400W each. Before approving the deployment, what capacity check is mandatory?

Accepted Answer

Confirming that available power, cooling, space, and network port capacity can support the addition

Answer

A proper capacity check before any significant deployment must validate all four constraints: power (80 kW total new load must fit within available PDU and UPS headroom), cooling (thermal load increase must be absorbable), physical space (rack space and floor loading), and network (switch ports, patch panels). Approving only one dimension without checking the others leads to stranded capacity or deployment failures.

CDCP - Certified Data Centre Professional Practice Test

CDCP - Certified Data Centre Professional Practice Test

CDCP Capacity Planning and Power Budgeting