Replace root volumes during instance refresh - Amazon EC2 Auto Scaling

Replace root volumes during instance refresh

Root volume replacement updates your instances by replacing only the root EBS volume while keeping the instance running. This removes the need to launch new instances and avoids potential capacity constraints. This process preserves all other instance resources including:

  • Network interfaces and IP addresses

  • Non-root EBS volumes

  • Instance store volumes and data

  • Security groups and IAM roles

During root volume replacement, your application continues running on the existing instance. The original root volume is detached, a new root volume is created from your specified AMI, and then attached to the same instance. Original root volumes are automatically deleted after successful replacement.

When you use the replace root volume strategy, instances go through these lifecycle states:

  1. ReplacingRootVolume - Root volume replacement begins

  2. ReplacingRootVolume:Wait - Waits for lifecycle hook completion (if configured)

  3. ReplacingRootVolume:Proceed - Proceeds with replacement

  4. RootVolumeReplaced - Replacement completed successfully

After root volume replacement completes, Auto Scaling conducts health checks on updated instances. If root volume replacement fails for an instance, Auto Scaling marks that instance for termination and replaces it with a new instance.