Amazon Elastic Compute Cloud
User Guide for Windows Instances

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Host Recovery

Host recovery automatically restarts your instances on to a new replacement host if failures are detected on your Dedicated Host. Host recovery reduces the need for manual intervention and lowers the operational burden if there is an unexpected Dedicated Host failure.

Additionally, built-in integration with AWS License Manager automates the tracking and management of your licenses if a host recovery occurs.

Note

AWS License Manager integration is supported only in Regions in which AWS License Manager is available.

Host Recovery Basics

Host recovery uses host-level health checks to assess Dedicated Host availability and to detect underlying system failures. Examples of problems that can cause host-level health checks to fail include:

  • Loss of network connectivity

  • Loss of system power

  • Hardware or software issues on the physical host

When a system failure is detected on your Dedicated Host, host recovery is initiated and Amazon EC2 automatically allocates a replacement Dedicated Host. The replacement Dedicated Host receives a new host ID, but retains the same attributes as the original Dedicated Host, including:

  • Availability Zone

  • Instance type

  • Tags

  • Auto placement settings

After the replacement Dedicated Host is allocated, the instances are recovered on to the replacement Dedicated Host. The recovered instances retain the same attributes as the original instances, including:

  • Instance ID

  • Private IP addresses

  • Elastic IP addresses

  • EBS volume attachments

  • All instance metadata

If instances have a host affinity relationship with the impaired Dedicated Host, the recovered instances establish host affinity with the replacement Dedicated Host.

When all of the instances have been recovered on to the replacement Dedicated Host, the impaired Dedicated Host is released, and the replacement Dedicated Host becomes available for use.

When host recovery is initiated, the AWS account owner is notified by email and by an AWS Personal Health Dashboard event. A second notification is sent after the host recovery has been successfully completed.

Stopped instances are not recovered on to the replacement Dedicated Host. If you attempt to start a stopped instance that targets the impaired Dedicated Host, the instance start fails. We recommend that you modify the stopped instance to either target a different Dedicated Host, or to launch on any available Dedicated Host with matching configurations and auto-placement enabled.

If you are using AWS License Manager to track your licenses, AWS License Manager allocates new licenses for the replacement Dedicated Host based on the license configuration limits. If the license configuration has hard limits that will be breached as a result of the host recovery, the recovery process is not allowed and you are notified of the host recovery failure through an Amazon SNS notification. If the license configuration has soft limits that will be breached as a result of the host recovery, the recovery is allowed to continue and you are notified of the limit breach through an Amazon SNS notification. For more information about setting license configuration limits, see Using License Configurations in the AWS License Manager User Guide.

Configuring Host Recovery

You can configure host recovery at the time of Dedicated Host allocation, or after allocation using the Amazon EC2 console or AWS Command Line Interface (CLI).

Enabling Host Recovery

You can enable host recovery at the time of Dedicated Host allocation or after allocation.

For more information about enabling host recovery at the time of Dedicated Host allocation, see Allocating Dedicated Hosts.

To enable host recovery after allocation (Console)

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. In the navigation pane, choose Dedicated Hosts.

  3. Select the Dedicated Host for which to enable host recovery, and then choose Actions, Modify Host Recovery.

  4. For Host recovery, choose Enable, and then choose Save.

To enable host recovery after allocation (AWS CLI)

Use the modify-hosts command and specify the host-recovery parameter.

$ aws ec2 modify-hosts --host-recovery on --host-ids h-1234567890

Disabling Host Recovery

You can disable host recovery at any time after the Dedicated Host has been allocated.

To disable host recovery after allocation (Console)

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. In the navigation pane, choose Dedicated Hosts.

  3. Select the Dedicated Host for which to disable host recovery, and then choose Actions, Modify Host Recovery.

  4. For Host recovery, choose Disable, and then choose Save.

To disable host recovery after allocation (AWS CLI)

Use the modify-hosts command and specify the host-recovery parameter.

$ aws ec2 modify-hosts --host-recovery off --host-ids h-1234567890

Viewing Host Recovery Configuration

You can view the host recovery configuration for a Dedicated Host at any time.

To view the host recovery configuration for a Dedicated Host (Console)

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. In the navigation pane, choose Dedicated Hosts.

  3. Select the Dedicated Host, and in the Description tab, review the Host Recovery field.

To view the host recovery configuration for a Dedicated Host (AWS CLI)

Use the describe-hosts command.

$ aws ec2 describe-hosts --host-ids h-1234567890

The HostRecovery response element indicates whether host recovery is enabled or disabled.

Host Recovery States

When a Dedicated Host failure is detected, the impaired Dedicated Host enters the under-assessment state, and all of the instances enter the impaired state. You cannot launch instances on to the impaired Dedicated Host while it is in the under-assessment state.

After the replacement Dedicated Host is allocated, it enters the pending state. It remains in this state until the host recovery process is complete. You cannot launch instances on to the replacement Dedicated Host while it is in the pending state. Recovered instances on the replacement Dedicated Host remain in the impaired state during the recovery process.

After the host recovery is complete, the replacement Dedicated Host enters the available state, and the recovered instances return to the running state. You can launch instances on to the replacement Dedicated Host after it enters the available state. The original impaired Dedicated Host is permanently released and it enters the released-permanent-failure state.

If the impaired Dedicated Host has instances that do not support host recovery, such as instances with instance store-backed volumes, the Dedicated Host is not released. Instead, it is marked for retirement and enters the permanent-failure state.

Supported Instance Configurations

Host recovery is supported only on Dedicated Hosts that are configured for instances with the following characteristics:

  • Use any instance type, except C5d, M5d, R5d, F1, H1, D2, I2, I3, I3en, P3dn, Z1d, and bare metal instances

  • Run in an Amazon VPC

  • Use Amazon EBS volumes only

    Note

    If the impaired Dedicated Host has instances with block device mappings for instance store volumes that do not support host recovery, they remain on the impaired Dedicated Host and are not automatically recovered on to the replacement Dedicated Host during recovery. As a remedial measure, the impaired Dedicated Host is marked for retirement and you receive a retirement notification after the host recovery is complete. Follow the remedial steps described in the retirement notification within the specified time period to manually recover the remaining instances on the impaired Dedicated Host. For more information, see Manually Recovering Unsupported Instances.

Manually Recovering Unsupported Instances

Host recovery does not support recovering instances that use instance store volumes. Follow the instructions below to manually recover any of your instances that could not be automatically recovered.

Warning

Data on instance store volumes is lost when an instance is stopped or terminated. This includes instance store volumes that are attached to an instance that has an EBS volume as the root device. To keep data from instance store volumes, back it up to persistent storage before the instance is stopped or terminated.

Manually Recovering EBS-Backed Instances

For EBS-backed instances that could not be automatically recovered, we recommend that you manually stop and start the instances to recover them onto a new Dedicated Host. For more information about stopping your instance, and about the changes that occur in your instance configuration when it's stopped, see Stop and Start Your Instance.

Manually Recovering Instance Store-Backed Instances

For instance store-backed instances that could not be automatically recovered, we recommend that you do the following:

  1. Launch a replacement instance on a new Dedicated Host from your most recent AMI.

  2. Migrate all of the necessary data to the replacement instance.

  3. Terminate the original instance on the impaired Dedicated Host.

Dedicated Host integrates with the following AWS services:

  • AWS License Manager—Tracks licenses across your Amazon EC2 Dedicated Hosts (supported only in Regions in which AWS License Manager is available). For more information, see the AWS License Manager User Guide.

Pricing

There are no additional charges for using host recovery, but the usual Dedicated Host charges apply. For more information, see Amazon EC2 Dedicated Hosts Pricing.

As soon as host recovery is initiated, you are no longer billed for the impaired Dedicated Host. Billing for the replacement Dedicated Host begins only after it enters the available state.

If the impaired Dedicated Host was billed using the On-Demand rate, the replacement Dedicated Host is also billed using the On-Demand rate. If the impaired Dedicated Host had an active Dedicated Host Reservation, it is transferred to the replacement Dedicated Host.