- LPU MCA Semester 1
- CAP470
- Unit 7
CAP470 · Unit 7: Cloud application design and collaboration
Introduction to green cloud
10 practice questions · in the ETE syllabus
Key points
- Green cloud reduces energy use and environmental impact
- Consolidation, elastic scaling and renewables
- PUE = total energy / IT energy; lower is better
- Efficient cooling and hardware reuse
Green cloud computing aims to reduce the energy use and environmental impact of cloud data centres. Main techniques:
| Technique | How it helps |
|---|---|
| Virtualisation and consolidation | Several virtual machines share one server, so fewer servers draw power |
| Elastic scaling | Capacity is released when demand falls |
| Renewable energy | Solar and wind reduce carbon emissions |
| Efficient cooling | Outside air, liquid cooling and good airflow cut cooling energy |
| Hardware reuse and recycling | Less electronic waste |
Power usage effectiveness (PUE) measures efficiency: total facility energy divided by the energy used by IT equipment. With 300 kWh total and 200 kWh for IT, PUE = 300 / 200 = 1.5. A PUE of 1.0 is the ideal, so lower is better. Consolidating ten 300 W servers onto four saves (10 - 4) x 300 = 1800 W.
Exam trap: PUE is a ratio without units and is always at least 1. A lower value means a more efficient data centre.
Try two questions
How does elastic scaling support green cloud goals?
- Resources are released when demand falls, so idle servers use less energy
- Servers are kept running at full speed at all times
- Applications are made to use as many servers as possible
- Customers are asked to stop using the cloud at night
Show the answer
A. Matching capacity to demand avoids energy spent on idle machines.
Why not B: Elasticity reduces waste.
Why not C: Using more servers wastes energy.
Why not D: Elasticity adjusts resources automatically.
Which energy source choice makes a data centre greener?
- Powering it only with diesel generators
- Powering it with renewable sources such as solar or wind
- Switching it off during daytime
- Using the oldest and least efficient servers
Show the answer
B. Renewable energy cuts the carbon footprint of the facility.
Why not A: Diesel generators increase emissions.
Why not C: Switching off would stop the service.
Why not D: Old servers waste energy.