Preparing for failover - AWS Elastic Disaster Recovery

Preparing for failover

In order to be able to launch your recovery instances quickly, you should preconfigure how those instances are to be launched and perform drills in order to make sure that all of your network and application settings are properly configured. You can configure how your instances will be launched by editing the Launch settings for each source server. Launch settings can be configured immediately when a source server has been added to AWS DRS, there is no need to wait for the initial sync process to finalize. Performing frequent drills is key for failover preparedness. Elastic Disaster Recovery makes it easy for you to launch drill instances as frequently as you want. Drills are nondisruptive – they do not impact the source server or ongoing data replication. If you experience a disaster in the middle of a drill, you can launch a new recovery instance from the source server's current state.

Configuring your launch settings

Before you can launch drill and recovery instances, you must configure your launch settings. Learn more about configuring launch settings.

Performing drills

After you have added all of your source servers and configured their launch settings, you are ready to launch a Recovery drill. It is crucial to drill the recovery of your source servers to AWS prior to initiating a Recovery in order to verify that your source servers function properly within the AWS environment.


It is crucial to perform a meaningful drill. For example, if you have a multi-server application, it's not enough to see that those servers launched as EC2 instances, it's crucial to see that they communicate, boot, and so on, so that in the case of a disaster they can achieve their desired RTO. Depending on what your system is, a meaningful test could be either ensuring that your server has booted, ranging to running your applications. At a minimum, ensure that your servers have their networking correctly configured. It is a best practice to perform drills regularly. After launching recovery drill instances, use either SSH (Linux) or RDP (Windows) to connect to your instance and ensure that everything is working correctly.

You can drill one source server at a time, or simultaneously drill multiple source servers. For each source server, you will be informed of the success or failure of the launch of your drill instances, including whether it has achieved the first boot. This is often not enough to determine whether you are prepared for a disaster. You can drill your source server as many times as you want. Each new drill first deletes any previously launched Recovery instance and dependent resources. After the drill, data replication continues as before. The new and modified data on the source server is transferred to the staging area subnet and not to the recovery instances that were launched during the test.


Windows source servers need to have at least 2 GB of free disk space to successfully launch a recovery instance.


Take into consideration that once a recovery instance is launched, other resources will be used in your AWS account and you will be billed for these resources. You should terminate launched recovery instances as soon as your drill is over in order to avoid unnecessary charges (primarily for Amazon EC2 and Amazon EBS).

Indicators that your source server is ready for a drill

Prior to launching a drill instance, ensure that your source servers are ready for testing by looking for the following indicators on the Source servers page:

  1. Under the Ready for recovery column, the server should show Ready. This means that initial sync has been completed and all data from the source server has been replicated to AWS.

  2. Under the Data replication status column, the server should show the Healthy status, but you can also launch the source server if the system is undergoing Lag or even Stall, but in that case the data may not be up to date. You can still launch a drill instance from a previous Point In Time.

  3. Under the Pending actions column, the server should show Initiate drill if no drill instances have ever been launched for the server. Otherwise, the column will be blank. This helps you identify whether the server has had a recent drill launch.

Launching drill instances

To launch a drill instance for a single source server or multiple source servers, go to the Source servers page and check the box to the left of each server for which you want to launch a drill instance.

Open the Initiate recovery job menu and select Initiate drill.

Select the Point in time snapshot from which to launch the drill instance for the selected source server. You can either select the Use most recent data option to use the latest snapshot available or select an earlier specific Point-in-time snapshot. You may opt to select an earlier snapshot in case you wish to return to a specific server configuration before a disaster occurred. After you have selected the Point in Time snapshot, click Initiate drill.

Learn more about Point in Time snapshots.

The AWS Elastic Disaster Recovery Console will indicate Recovery job is creating drill instance for X source servers when the drill has started.

Choose View job details on the dialog to view the specific Job for the test launch in the Recovery job history tab.

Successful drill instance launch indicators

You can tell that the Drill instance launch started successfully through several indicators on the Source servers page.

  1. The Last recovery result column will show the status of the recovery launch and the time of the launch. A successful drill instance launch will show the Successful status. A launch that is still in progress will show the Pending status.

  2. The launched Drill instance will also appear on the Recovery instances page.