Disaster Recovery — AWS Solutions Architect Associate Complete Course.
Chapter 24: AWS Disaster Recovery Fundamentals
We have reached one of the last chapters of the AWS Solutions Architect Associate Course! Today we are going to look at Disaster Recovery in AWS. Let’s imagine that, for whatever reason, an earthquake or tsunami occurs in a region where we host our servers, and our application stops working. In the case of an MVP or a minor application, it would not be so serious, but let’s imagine it is a business-critical application that affects our business considerably if it goes down. Let’s see the different Disaster Recovery strategies using Amazon Web Services!
Remember that you can find all the chapters from the course at the following link:
RPO AND RTO
When we talk about disaster recovery, we have to understand two fundamental concepts before defining the strategies:
- RPO (Recovery Point Objective) → Maximum amount of data — as measured by time — that can be lost after a recovery from a disaster
- RTO (Recovery Time Objective) → Metric that defines the time to recover your IT infrastructure and services following a disaster to ensure business continuity
DISASTER RECOVERY STRATEGIES
Disaster recovery strategies can be categorized into four approaches, ranging from the low cost and low complexity of making backups to more complex procedures.
BACKUP AND RESTORE
Backup & Restore is the most straightforward strategy to implement. On the one hand, it has a high RPO/RTO, but on the other hand, it’s the cheapest one. Using this strategy, you only need to frequently back up your data and restore it in the case of a disaster. In addition to data, you must redeploy the infrastructure, configuration, and application code in the recovery Region.
PILOT LIGHT
With the pilot light approach, you replicate your data from one Region to another and provide a copy of your core workload infrastructure (just the critical parts). Resources required to support data replication and back-ups, such as databases and object storage, are always on. Other elements, such as application servers, are switched off and are only used during disaster recovery failover, always having the option to quickly provision a full-scale production environment by switching on and scaling out your application servers.
WARM STANDBY
The warm standby approach ensures a scaled-down but functional copy of your production environment in another Region. So basically, your whole system will be active in a different region but smaller. In case of a disaster, we scale out.
This approach extends the pilot light concept and decreases the time to recovery because your workload is always-on in another Region.
MULTI-SITE ACTIVE/ACTIVE
Multi-Site active/active has the lowest RTO (reducing recovery time to near zero) but is way more expensive than the other options. For that reason, it’s recommendable for business-critical applications. In this case, you run your workload simultaneously in multiple Regions as part of a multi-site active/active strategy, allowing users to access your workload in any of the Regions in which it is deployed. In a disaster, we point to a different region using Route 53.
TYPICAL EXAM QUESTIONS
Honestly, in the AWS Solutions Architect Associate exam, there will not be many questions about Disaster Recovery; but in the case of appearing, they would be very similar to these:
A company plans to replicate a limited set of core services to the Disaster Recovery site, ready to take over seamlessly during a disaster. The company will switch off all other services. Which Disaster Recovery should the company use?
- Backup and restore
- Pilot light
- Warm standby
- Multi-site
Solution: 2. With the pilot light approach, you replicate your data from one region to another and provide a copy of your core workload infrastructure (just the critical parts). Resources required to support data replication and back-ups, such as databases and object storage, are always on. Other elements, such as application servers, are switched off and are only used during disaster recovery failover, always having the option to quickly provision a full-scale production environment by switching on and scaling out your application servers.
A company plans to keep its core business-critical systems running in the Disaster Recovery cloud. Other services can be replicated but switched off. Which Disaster Recovery strategy should the company use?
- Backup and restore
- Pilot light
- Warm standby
- Multi-site
Solution: 3. In a warm standby scenario, a scaled-down version of a fully functional environment is always running in the cloud. When a disaster happens, the system quickly scales up to handle the production load. It extends the pilot light solution. You can read more about the Disaster Recovery Strategies at the following link.
A company needs to ensure they can seamlessly failover between AWS Regions in the event of a disaster with minimal downtime and data loss. The applications will run in an active-active configuration. Which Disaster Recovery strategy should the company use?
- Backup and restore
- Pilot light
- Warm standby
- Multi-site
Solution: 4. In a multi-site strategy, the system runs in more than one location, each capable of handling the full production workload. This model, often known as an active-active configuration, is the most expensive but provides the highest level of availability, with zero downtime and near zero loss.
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