Capacity Rebalancing
Capacity Rebalancing is a feature used to proactively maintain the balanced distribution of instances across multiple Availability Zones within an Auto Scaling group. It helps to minimize the risk of decreased capacity due to interruptions such as scheduled maintenance, hardware failure, or software issues by redistributing on-demand instances that are close to being interrupted. It works in conjunction with Amazon EC2 Auto Scaling's rebalancing algorithm, which helps ensure that your application maintains its desired level of availability, even as it scales in response to changing conditions.
Guide: Capacity Rebalancing - AWS Solution Architect
What is Capacity Rebalancing?
Capacity Rebalancing is a feature in AWS Auto Scaling that continuously monitors the health of instances and automatically replaces instances that are at risk. It is associated with AWS EC2 Auto Scaling and EC2 Spot instances. It facilitates maintaining application availability during Spot instance interruptions.
Why is it Important?
Capacity rebalancing is crucial as it helps maintain the performance and availability of applications hosted on AWS. It reduces the risk of workload disruption by foreseeing spot instance interruptions and launching a replacement instance before the existing instance is interrupted.
How it Works?
When AWS predicts an interruption for a spot instance within the auto-scaling group, capacity rebalancing first tries to launch a replacement instance. Once the new instance is in a running state, it then proceeds to terminate the instance that received the interruption warning.
Exam Tips: Answering Questions on Capacity Rebalancing
1. Understand the purpose of Capacity Rebalancing in maintaining application availability.
2. Be clear about the relationship between Capacity Rebalancing, EC2 Auto Scaling, and Spot Instances.
3. Know the process of how Capacity Rebalancing preemptively replaces instances.
4. Remember that Capacity Rebalancing does not eliminate Spot Interruptions but rather reduces their impact by maintaining instance capacity.
Note: In the exam, look for keywords that indicate a need for high availability, cost-effectiveness (spot instances), and automatic replacement of instances.
AWS Certified Solutions Architect - Auto Scaling Example Questions
Test your knowledge of Amazon Simple Storage Service (S3)
Question 1
In a company's architecture, a critical application is running on Spot Instances within an Auto Scaling group. The Solutions Architect wants to improve performance and mitigate the risks of Spot Instances being terminated suddenly. What should they do?
Question 2
As a Solutions Architect, you notice that instance interruptions are causing capacity issues in your application's backend. The application is hosted on Spot Instances. What action should you take to maintain a consistent capacity?
Question 3
A Solutions Architect needs to design a data processing architecture that needs to be cost-effective, uses Spot Instances, and minimizes data processing disruptions. Which solution will best fit this requirement?
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