Learn how to design a reliable web application on Amazon EC2 by leveraging AWS Availability Zones. Discover why spreading EC2 instances across multiple zones ensures fault tolerance, high availability, and business continuity.
Table of Contents
Question
A company wants to design a reliable web application hosted on Amazon EC2. Which approach will achieve this goal?
A. Launch large EC2 instances in the same Availability Zone.
B. Spread EC2 instances across more than one security group.
C. Spread EC2 instances across more than one Availability Zone.
D. Use an Amazon Machine Image (AMI) from the AWS Marketplace.
Answer
C. Spread EC2 instances across more than one Availability Zone.
Explanation
The approach that will achieve the goal of designing a reliable web application hosted on Amazon EC2 is to spread the EC2 instances across more than one Availability Zone. An Availability Zone is a physically isolated location within an AWS Region that has its own power, cooling, and network connectivity. By spreading EC2 instances across multiple Availability Zones, users can increase the fault tolerance and availability of their web applications, while reducing latency for end-users.
AWS Availability Zones (AZs) are isolated data centers within a specific AWS Region, designed to ensure high availability and fault tolerance. Each AZ operates independently with its own power, cooling, and networking infrastructure but is interconnected with other AZs in the same region through low-latency links. This setup allows for seamless failover and redundancy in case of disruptions in one AZ.
By distributing EC2 instances across multiple AZs, you can achieve the following benefits:
- Fault Tolerance: If one AZ goes offline due to hardware failure or natural disasters, the application can continue running in other AZs without service interruption.
- High Availability: Spreading instances across AZs ensures that your application remains accessible even during outages in a single zone.
- Scalability: Resources can be scaled within and across AZs to handle varying traffic loads dynamically.
Why Other Options Are Incorrect
A. Launch large EC2 instances in the same Availability Zone: This does not provide redundancy or fault tolerance because all resources are confined to a single point of failure.
B. Spread EC2 instances across more than one security group: Security groups control access to instances but do not address availability or fault tolerance.
D. Use an Amazon Machine Image (AMI) from the AWS Marketplace: While AMIs simplify instance deployment, they do not inherently improve reliability or availability.
Best Practices for Reliability
- Use Elastic Load Balancing (ELB) to distribute traffic across multiple AZs.
- Implement Auto Scaling Groups to automatically adjust the number of instances based on demand.
- Deploy databases with multi-AZ configurations (e.g., Amazon RDS) for redundancy.
- Monitor health using services like Amazon CloudWatch and implement automated failover mechanisms.
Spreading resources across multiple AZs is a cornerstone of AWS’s reliability and high availability design principles, ensuring your web application can withstand failures and maintain business continuity.
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