Dedicated Host (DDH) is a single-tenant physical server that is running on the Alibaba Cloud virtualization platform. This topic describes the features of DDH.

Automatic deployment

The automatic deployment function can help you automatically select a dedicated host to deploy ECS instances. After a dedicated host is set to allow automatic deployment, it resides in the resource pool for automatic deployment in your account. You do not need to specify a dedicated host when you create an ECS instance. The system automatically selects a dedicated host from the resource pool to deploy the ECS instance. For more information about how to enable automatic deployment, see Set the dedicated host to enable automatic deployment.

The following table describes the application scenarios of the automatic deployment function.
Scenario Operation Result Reference
Create an ECS instance. Specify a dedicated host. The ECS instance is deployed on the specified dedicated host.
Select Automatic Deployment ECS instances are automatically deployed.
Migrate an ECS instance to a dedicated host from a shared host. Specify a dedicated host. The ECS instance is deployed on the specified dedicated host.
Do not specify a dedicated host. ECS instances are automatically deployed.
Migrate ECS instances between dedicated hosts. Specify a dedicated host. The ECS instance is deployed on the specified dedicated host.
Do not specify a dedicated host. ECS instances are automatically deployed.
Note If the dedicated host where the ECS instance is located allows automatic deployment and has the most available resources, the ECS instance is still placed on the current dedicated host.

Host association

The host association feature is applicable to ECS instances that have enabled the no fees for stopped instances feature. You can specify whether an instance is placed on the original dedicated host after it has been stopped and restarted. After the host is associated, even if your ECS instance is scheduled to shut down, you can still ensure that the instance runs on the same physical server when it is restarted. This feature also helps you maintain the same deployment policy for the ECS instance.

The following table describes how to use the host association feature.
Scenario Operation Result
An ECS instance has enabled the no fees for stopped instances feature, and the instance is started again after it is stopped. Enable the host association feature.

For more information, see Associate an ECS instance with a dedicated host.

The ECS instance is still deployed on the original dedicated host. If the available resources of the original dedicated host are insufficient, the instance fails to be restarted.
Disable the host association feature.

For more information, see Associate an ECS instance with a dedicated host and set Associate with DDH to No to disable this feature.

The ECS instance is first deployed on the original dedicated host. If the available resources of the original dedicated host are insufficient, the system automatically deploys the ECS instance on another dedicated host.

Resource efficiency

If the no fees for stopped instances feature is enabled, when you stop a instance, the CPU and memory resources used by the instance are released.

For more information about the deployment process when the instance is restarted, see Application scenarios of associating a dedicated host.