CDCS

Review 59 CDCS practice questions with answer explanations and community insights.

Question 1

A 5kW (power consumption) server keeps crashing with the message ‘temperature too high’. - The intake temperature is measured at 25 °C/77 °F and a relative humidity (RH) level of 50%. - The exhaust temperature is 29 °C/84 °F and 45% RH. - The raised floor is providing adequate amount of CFM/CMH at a reasonable velocity. - The pressure under the raised floor is approximately 25 Pa/0.1 inch H20. Analyze the situation and indicate what the most likely cause is for this server to crash.

  1. Dust inside the server causing issues with convection-based heat transfer
  2. The exhaust temperature is exceeding the ASHRAE recommended values
  3. The raised floor pressure is too low and/or the raised floor tile % opening is not adequate
  4. No cause could be determined as the CFM/CMH of the air conditioning equipment is not stated

Question 2

What is the main disadvantage of using a ToR (Top of Rack) design?

  1. A single ToR (Top of Rack) switch is more expensive than an EoR (End of Row) switch.
  2. You need a separate rack to install all your ToR (Top of Rack) switches.
  3. There will be more switches to manage.
  4. A ToR (Top of Rack) switch has only optical interfaces.

Question 3

The location of a data center is just above the Arctic Circle (North Pole). The outside air temperature is never above 21 °C/70 °F. Taking energy efficiency as the highest priority, which cooling system should you recommend?

  1. Standard air conditioning units, as spares might be not readily available
  2. Any cooling system can be efficient, because the outside air temperature will not influence the temperature of the air intake of the ICT equipment
  3. Waterside economizer
  4. Airside economizer

Question 4

When are the wet bulb’s and dry bulb’s temperature identical?

  1. When the dry bulb’s temperature is at the lowest allowable temperature for IT equipment as per the ASHRAE
  2. When the dry bulb’s temperature is at the highest allowable temperature for IT equipment as per the ASHRAE
  3. When the relative humidity is at the best practice value for relative humidity, being 50% RH
  4. When the relative humidity is 100%

Question 5

An air-conditioner unit needs to be selected. Two types are available: - Unit-A has a Sensible Heat Ratio (SHR) of 0.7. - Unit-B has a Sensible Heat Ratio (SHR) of 0.9. From an efficiency point of view, which one should be selected?

  1. It does not matter, as the Sensible Heat Ratio has nothing to do with efficiency.
  2. Not relevant, as Sensible Heat Ratio is only specified for air-conditioner equipment to indicate the ratio between intake temperature and exhaust temperature.
  3. Unit A
  4. Unit B
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