Tutorial / Cram Notes
Disaster recovery (DR) strategies are essential for maintaining business continuity in the face of adverse events, such as natural disasters, system failures, or cyber attacks. For enterprises using cloud services like AWS, aligning disaster recovery practices with the cloud infrastructure is critical to ensure resilience and fast recovery times.
In this context, AWS provides various services and strategies that can be tailored to an organization’s specific recovery objectives, such as Recovery Time Objective (RTO) and Recovery Point Objective (RPO). Below, we’ll explore some of the common disaster recovery strategies using AWS services.
AWS Elastic Disaster Recovery (DRS)
AWS Elastic Disaster Recovery (formerly AWS CloudEndure Disaster Recovery) is a service that helps businesses quickly recover their systems and data to AWS from physical, virtual, or cloud-based infrastructures, minimizing downtime and data loss. It enables continuous replication of your live environment to a low-cost staging area in AWS, which can be spun up rapidly in an emergency.
For example, if you have a live database server, Elastic Disaster Recovery can replicate it into a staging environment. In the event of a disaster, you can execute a failover, which allows you to switch to the replica and have your database back online with minimal disruption.
Pilot Light
The pilot light method involves keeping a minimal version of an environment running in the cloud. This method is similar to a standby generator that is always ready to assume a full workload if needed. In AWS, this might involve having key services such as database servers continuously running in a standby state, with data replication to keep them up-to-date.
An example of a pilot light scenario is keeping a read replica of your database in AWS while the majority of your infrastructure remains on-premise. In case of failure, you can promote the read replica to a primary database and redirect traffic to AWS.
Warm Standby
A warm standby approach takes pilot light a step further. In this strategy, a scaled-down but fully functional version of the environment is always running in the cloud. This allows for a quicker recovery time since systems are already up and running, and only scaling is required.
For example, if an application stack typically consists of multiple web servers, an application server, and a database server, a warm standby might maintain one web server and a smaller version of the database server running on AWS. If a disaster occurs, you can scale these services automatically using AWS Auto Scaling to match the production load.
Multi-site
The multi-site strategy is designed for applications that require extremely high availability. This approach involves running a full-scale production environment across multiple geographically dispersed AWS regions. Data is replicated in real time, ensuring near-zero RPO and RTO.
For example, a multi-site setup might involve running your application across two AWS regions, with Route 53 managing the traffic across both sites. If one region experiences an outage, traffic can be rerouted to the unaffected region with no perceived downtime for the user.
Comparison of DR Strategies
| Strategy | RTO | RPO | Cost | Complexity | Use Case |
|---|---|---|---|---|---|
| Elastic DR | Low | Low | Medium | Moderate | Suitable for mixed and complex environments |
| Pilot Light | Medium | Low | Low | Low | Ideal for critical core applications |
| Warm Standby | Low | Low | High | Moderate | Perfect for critical applications with variable traffic |
| Multi-site | Near 0 | Near 0 | Highest | High | Essential for mission-critical, high-traffic apps |
When preparing for the AWS Certified Solutions Architect – Professional exam, candidates must be familiar with these strategies and know how to design and implement them according to best practices and specific business requirements. Understanding the trade-offs between cost, complexity, and speed of recovery allows architects to make informed decisions when designing disaster recovery plans on AWS.
Practice Test with Explanation
True or False: AWS Elastic Disaster Recovery (DRS) only supports recovery of on-premises workloads to AWS.
- A) True
- B) False
Answer: B) False
Explanation: AWS Elastic Disaster Recovery (DRS) supports both on-premises workloads and EC2-based workloads, allowing you to replicate to AWS for disaster recovery purposes.
Which of the following strategies involves the least downtime in case of a disaster?
- A) Pilot Light
- B) Warm Standby
- C) Backup and Restore
- D) Multi-Site
Answer: D) Multi-Site
Explanation: The Multi-Site strategy involves an active-active configuration where full-scale versions of a workload run in two or more locations simultaneously, providing seamless failover with the least downtime.
True or False: The Warm Standby strategy is more cost-efficient than the Multi-Site strategy.
- A) True
- B) False
Answer: A) True
Explanation: The Warm Standby strategy involves running a scaled-down version of the workload, which is more cost-efficient compared to running full-scale versions in the Multi-Site approach.
In the context of AWS disaster recovery, what does the “Pilot Light” method use to minimize data recovery times?
- A) Frequent backups to Amazon S3
- B) A large EC2 instance running 24/7
- C) Core pieces of your system running and continually updated
- D) Manual processes for recovery
Answer: C) Core pieces of your system running and continually updated
Explanation: The Pilot Light strategy keeps critical core elements of your system running on AWS to speed up recovery time. Data and application updates are continuously replicated, enabling a quick scale-up in case of a disaster.
True or False: AWS Elastic Disaster Recovery (DRS) does not support disaster recovery automation.
- A) True
- B) False
Answer: B) False
Explanation: AWS Elastic Disaster Recovery (DRS) supports automation for the recovery process, including replication, failover, and failback actions to meet recovery objectives.
Which AWS service primarily deals with the orchestration of backups across AWS services for disaster recovery purposes?
- A) AWS Backup
- B) AWS Elastic Disaster Recovery
- C) AWS Storage Gateway
- D) AWS Systems Manager
Answer: A) AWS Backup
Explanation: AWS Backup is designed to centralize and automate data protection across AWS services, making it easier to manage and orchestrate backups for disaster recovery.
True or False: The Pilot Light approach is more appropriate for workloads with very low tolerance for downtime than the Backup and Restore approach.
- A) True
- B) False
Answer: A) True
Explanation: The Pilot Light approach maintains a minimal version of the environment, reducing the time and effort required to bring a full workload online, making it more suitable for low downtime tolerance than Backup and Restore, which requires restoration from backups.
True or False: To implement a Multi-Site strategy, an application must be designed for high availability and state synchronization across sites.
- A) True
- B) False
Answer: A) True
Explanation: Multi-Site strategy requires the application to be designed to handle running in multiple locations with synchronization to maintain state, ensuring high availability.
Which disaster recovery strategy is typically associated with the highest cost?
- A) Pilot Light
- B) Warm Standby
- C) Backup and Restore
- D) Multi-Site
Answer: D) Multi-Site
Explanation: Multi-Site, which involves running fully operational environments in more than one location, typically incurs the highest cost due to the need for more resources.
True or False: AWS Elastic Disaster Recovery (DRS) supports point-in-time recovery of instances and volumes.
- A) True
- B) False
Answer: B) False
Explanation: AWS Elastic Disaster Recovery (DRS) continuously replicates your data to AWS, allowing for minimal data loss, but it does not typically offer point-in-time recovery, which is a feature more commonly associated with database services like Amazon RDS.
Select the disaster recovery strategy that is NOT directly offered by AWS services:
- A) Pilot Light
- B) Warm Standby
- C) Multi-Site
- D) Cold Site
Answer: D) Cold Site
Explanation: While AWS services can be used to implement Cold Site strategies, AWS does not directly offer a “Cold Site” disaster recovery strategy as a service. Customers can create similar setups using Amazon EC2 and other services on an as-needed basis.
True or False: AWS recommends that you regularly test your disaster recovery plan to ensure it meets your business objectives.
- A) True
- B) False
Answer: A) True
Explanation: AWS advises to periodically test disaster recovery plans to validate that they meet recovery objectives and to familiarize the team with disaster recovery procedures.
Interview Questions
What is AWS Elastic Disaster Recovery, and how does it differ from traditional disaster recovery solutions?
AWS Elastic Disaster Recovery (formerly known as AWS DRS) is a service that helps quickly recover your systems and applications from a disaster scenario. It differs from traditional solutions by providing cloud-native, flexible, and cost-effective capabilities to replicate and recover workloads from anywhere to AWS. It uses continuous replication, allowing you to achieve low recovery point objectives (RPO) and recovery time objectives (RTO).
Could you explain the “pilot light” disaster recovery strategy and when it is most appropriate to use?
The “pilot light” strategy involves a minimal version of an environment always running in the cloud. It typically includes critical core elements such as databases, with the data continuously replicated to this minimal footprint. It is most appropriate for scenarios where the recovery speed is critical but where businesses are looking to minimize costs by not running a full-scale environment continuously.
What is a “warm standby” approach in disaster recovery, and how does it ensure business continuity?
A “warm standby” approach consists of having a scaled-down but fully functional version of the full system running in the cloud at all times. It ensures business continuity by allowing for a quicker failover because the standby system can be scaled up to handle production load within minutes.
Describe the multi-site strategy of disaster recovery.
The multi-site strategy involves running a full-scale production environment in multiple separate geographic locations (regions or availability zones). This could be a fully active-active or active-passive setup. The advantage is that if one site goes down, the other can take over immediately, with minimal or no disruption to the service.
How does AWS Elastic Disaster Recovery handle cross-region replication?
AWS Elastic Disaster Recovery enables cross-region replication by continuously copying your machines’ disks to the AWS region of your choice, where they are stored EBS snapshots. In the event of a disaster or disruption in the primary site or region, this allows you to quickly recover your applications in a different AWS region.
What are Recovery Point Objective (RPO) and Recovery Time Objective (RTO), and why are they important in disaster recovery planning?
RPO is the maximum tolerable period in which data might be lost due to a major incident, and RTO is the goal for the maximum allowable downtime after a disaster. They are critical in disaster recovery planning to ensure that the business impact remains acceptable and to define appropriate strategies and investment in disaster recovery capabilities.
When designing a disaster recovery solution, what AWS services can be used to automate failover?
AWS services that can be used to automate failover include AWS Route 53 for DNS failover, Amazon CloudWatch in combination with AWS Lambda and SNS for automatic alerts and triggers, and AWS Auto Scaling to automatically adjust resources based on demand.
How would you secure data during the disaster recovery process using AWS services?
To secure data during the disaster recovery process, I would use a combination of AWS KMS for encryption key management, encrypt data at rest using Amazon EBS encryption or S3 SSE, and ensure that data in transit is protected using TLS across AWS services.
What factors should you consider when determining the appropriate frequency for data backups as part of a disaster recovery plan?
Factors include the criticality of data, rate of change, RPO and RTO requirements, regulatory compliance needs, and the impact on performance or user experience during the backup process.
Explain how AWS CloudFormation can benefit disaster recovery planning and orchestration.
AWS CloudFormation allows you to automate infrastructure provisioning with Infrastructure as Code (IaC). It is beneficial for disaster recovery scenarios since it ensures consistent, fast, and repeatable infrastructure setup, which is crucial for quick recovery from disasters.
What are the advantages of using Amazon S3 cross-region replication in a disaster recovery setup?
Amazon S3 cross-region replication (CRR) provides advantages such as geographical diversification, which protects against region-wide outages, the ability to meet compliance requirements for data locality, and improved latency with closer proximity to end-users in multiple regions.
Can you describe how AWS Elastic Disaster Recovery integrates with AWS Organizations for managing disaster recovery across multiple accounts?
AWS Elastic Disaster Recovery can integrate with AWS Organizations to provide a centralized and streamlined disaster recovery solution across multiple AWS accounts. It allows you automate replication policies, centralize recovery plans, and manage the disaster recovery lifecycle for all accounts within the organization.
Great read on disaster recovery strategies. Very informative for the SAP-C02 exam prep!
Can someone explain the differences between pilot light and warm standby?
I have been using AWS Elastic Disaster Recovery for a while, and it’s quite reliable.
Thanks for the post, it helped me a lot!
How does AWS Elastic Disaster Recovery compare to multi-site in terms of cost?
I appreciate the detailed explanation on disaster recovery.
Has anyone deployed a warm standby environment? Any tips?
Interesting post, but it’s too high level in some parts.