These modules are broken down into the AWS Disaster Recovery strategies. All the modules make use of the Unishop application and each module will highlight the AWS strategy and AWS services that have features that make it easy to implement a disaster recovery plan.
Module 1: Backup and Restore. Backup and restore is a suitable approach for mitigating against data loss or corruption. This approach can also be used to mitigate against a regional disaster by replicating data to other AWS Regions, or to mitigate lack of redundancy for workloads deployed to a single Availability Zone. In addition to data, you must redeploy the infrastructure, configuration, and application code in the recovery Region. To enable infrastructure to be redeployed quickly without errors, you should always deploy using infrastructure as code (IaC) using services such as AWS CloudFormation or the AWS Cloud Development Kit (CDK). Without IaC, it may be complex to restore workloads in the recovery Region, which will lead to increased recovery times and possibly exceed your RTO. In addition to user data, be sure to also back up code and configuration, including Amazon Machine Images (AMIs) you use to create Amazon EC2 instances. You can use AWS CodePipeline to automate redeployment of application code and configuration.
Module 2: Pilot Light. With the pilot light approach, you replicate your data from one Region to another and provision a copy of your core workload infrastructure. Resources required to support data replication and backup, such as databases and object storage, are always on. Other elements, such as application servers, are loaded with application code and configurations, but are “switched off” and are only used during testing or when disaster recovery failover is invoked. In the cloud, you have the flexibility to deprovision resources when you do not need them, and provision them when you do. A best practice for “switched off” is to not deploy the resource, and then create the configuration and capabilities to deploy it (“switch on”) when needed. Unlike the backup and restore approach, your core infrastructure is always available and you always have the option to quickly provision a full scale production environment by switching on and scaling out your application servers.
Module 3: Warm Standby. The warm standby approach involves ensuring that there is a scaled down, but fully functional, copy of your production environment in another Region. This approach extends the pilot light concept and decreases the time to recovery because your workload is always-on in another Region. This approach also allows you to more easily perform testing or implement continuous testing to increase confidence in your ability to recover from a disaster.
Module 4: Hot Standby. You can run your workload simultaneously in multiple Regions as part of a multi-site active/active or hot standby active/passive strategy. Hot standby uses an active/passive configuration where users are only directed to a single region and DR regions do not take traffic. Most customers find that if they are going to stand up a full environment in the second Region, it makes sense to use it active/active.
AWS Elastic Disaster Recovery. AWS Elastic Disaster Recovery (DRS) continuously replicates server-hosted applications and server- hosted databases from any source into AWS using block-level replication of the underlying server. Elastic Disaster Recovery enables you to use a Region in AWS Cloud as a disaster recovery target for a workload hosted on-premises or on another cloud provider, and its environment. It can also be used for disaster recovery of AWS hosted workloads if they consist only of applications and databases hosted on EC2 (that is, not RDS). Elastic Disaster Recovery uses the Pilot Light strategy, maintaining a copy of data and “switched-off” resources in an Amazon Virtual Private Cloud (Amazon VPC) used as a staging area. When a failover event is triggered, the staged resources are used to automatically create a full-capacity deployment in the target Amazon VPC used as the recovery location.