Highly Available and Fault-Tolerant Architectures

This chapter covers the following topics:

• Comparing Architecture Designs

• Disaster Recovery and Business Continuity

• Automating AWS Architecture

• Elastic Beanstalk

This chapter covers content that’s important to the following exam domain/objective:

• Domain 1: Design Resilient Architectures

  Objective 1.2 Design highly available and/or fault-tolerant architectures

The terms high availability and fault tolerant take on unique meanings in today’s hosted cloud. Amazon wants to make sure that you understand how these terms differ in a cloud environment from in on-premises situation. For example, you might be accustomed to using clustering as a common method to protect database data. In the cloud, clustering has been mainly been replaced with horizontal scaling and placing multiple copies of databases in different data centers. You could still build a cluster in the cloud, but there are better ways to achieve high availability and fault tolerance—or at least Amazon and many customers feel there are better ways. Ultimately, no matter the terminology used, your application should be always up and available when the end user needs it. In addition, your data records should always be available. And both your application and your data should be able to handle problems in the backend; you need compute power for the many web servers that are available to take over, and your data needs to be stored in numerous physical locations.

The questions on the AWS Certified Solutions Architect - Associate (SAA-C02) exam quantify your understanding of the services at AWS that enable you to design your application stacks to be highly available and very fault tolerant.

“Do I Know This Already?” Quiz

The “Do I Know This Already?” quiz allows you to assess whether you should read this entire chapter thoroughly or jump to the “Exam Preparation Tasks” section. If you are in doubt about your answers to these questions or your own assessment of your knowledge of the topics, read the entire chapter. Table 3-1 lists the major headings in this chapter and their corresponding “Do I Know This Already?” quiz questions. You can find the answers in Appendix A, “Answers to the ‘Do I Know This Already?’ Quizzes and Q&A Sections.”

Table 3-1 “Do I Know This Already?” Section-to-Question Mapping

1. Which of the following is a characteristic of applications that are designed to be highly available?

   1. Minimal downtime

   2. Increased performance

   3. Higher level of security

   4. Cost-effective operation

2. Which of the following is a characteristic of applications that are designed with a high level of fault tolerance?

   1. Automatic recovery from most failures

   2. Higher speed

   3. Higher performance

   4. Cost-effective operation

3. What does the term RPO stand for?

   1. Reliability point objective

   2. Recovery point objective

   3. Restore point objective

   4. Return to an earlier phase of operation

4. What does the term RTO stand for?

   1. Recovery tier objective

   2. Recovery time objective

   3. The amount of data that will be lost

   4. The time the application will be down

5. What is the purpose of using CloudFormation?

   1. To recover from failures

   2. To automate the building of AWS infrastructure components

   3. To deploy applications with automation

   4. To document manual tasks

6. What CloudFormation component is used to check deployment changes to existing infrastructure?

   1. CloudFormation template

   2. Stack

   3. Change set

   4. JSON script

7. What two components does Elastic Beanstalk deploy?

   1. Infrastructure and storage

   2. Application and infrastructure

   3. Compute and storage

   4. Containers and instances

8. What term defines application updates that are applied to a new set of EC2 instances?

   1. Rolling

   2. Immutable

   3. All at once

   4. Blue/green