To minimize the impact of physical failures on your business, Alibaba Cloud provides the auto failover feature that enables the system to automatically migrate the Elastic Compute Service (ECS) instances deployed on a dedicated host if the dedicated host fails. This topic describes how to enable or disable auto failover for a dedicated host.
By default, Failover upon Host Failure is selected when you create a dedicated host. Unless you manually deselect this option, there is no need to enable it again.
Limits
ECS instances on local SSD type i2 dedicated hosts do not support self-service migration or automatic failover.
Usage notes
If a dedicated host with local SSDs fails, you can submit a ticket to request a migration. However, the data on local SSDs will be lost after the migration.
After all the ECS instances on a failed dedicated host are migrated to another dedicated host, the host ID and the metadata of the ECS instances remain unchanged. The metadata includes the ID, private IP address, and public IP address of each ECS instance. However, the machine ID of the dedicated host is changed.
If auto failover is disabled and your dedicated host fails, submit a ticket to apply for a new dedicated host.
Procedure
Log on to the ECS console.
In the left-side navigation pane, choose Instances & Images >
> Dedicated Hosts. In the top navigation bar, select the region and resource group to which the resource belongs.
Find the dedicated host that you want to manage, move the pointer over the name or ID of the dedicated host in the Host ID/Name column, and then click
next to the name of the dedicated host. In the Modify DDH Information dialog box, click
to turn on or turn off Auto Failover as needed. 
Click OK.
Result
On the Host tab, find the dedicated host and click Details in the Actions column. On the Host Details tab of the panel that appears, make sure that the Failover parameter is specified as expected. 