Tuesday, 8 January 2019

Difference between Fixed Performance and Burstable Performance in EC2 Instances (Fixed Performance vs Burstable Performance)

Following are the basic differences between Fixed Performance and Burstable Performance:

1. Performance Instances provide a consistent CPU performance whereas Burstable Performance Instances provide a baseline CPU performance under normal workload. But when the workload increases, Burstable Performance Instances have the ability to burst, i.e. increase the CPU performance.

2. CPU credit regulates the amount CPU burst of an instance. You can spend this CPU credit to increase the CPU performance during the burst period. 

Suppose you are operating the instance at 100% of CPU performance for 5 minutes, you will spend 5 (i.e. 5*1.0) CPU credits. Similarly if you run an instance at 50% CPU performance for 5 minutes you will spend 2.5 (i.e. 5*0.5) CPU credits.

3. When you create an instance, you will get an initial CPU credit. In every hour, you will get certain amount of CPU credits automatically (this amount depends on the type of instance). If you don't burst the CPU performance, the CPU credit will be added to your CPU Credit Balance of your account. 

4. CPU credit keeps carrying forward till 24 hours, after that it re-initializes. If you are out of CPU Credit (i.e. CPU Credit Balance turns into 0) your instance will work on baseline performance.

5. Baseline performance is just 30% for t2.large.

6. Not all EC2 instances support Burstable Performance.

7. Mainly used for micro-services, low-latency interactive applications, small and medium databases, virtual desktops, development, build, and stage environments, code repositories, and product prototypes.

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