Change instance types across zones - Elastic Compute Service

The cross-zone instance type change feature allows you to migrate an Elastic Compute Service (ECS) instance across zones in a region and change the instance type (vCPUs and memory) of the ECS instance to another instance type in the same instance family to meet your business requirements.

Scenarios

Change the instance type of an ECS instance
If the current configurations of your ECS instance cannot meet your business requirements and the required instance type is sold out in the current zone, you can change the instance type within the same instance family while migrating the ECS instance across zones.
Change the zone of an ECS instance
You can deploy your application on ECS instances across different zones in a region to ensure that when a zone fails, services can be quickly switched to another zone to continue running. This improves the overall availability and stability of your system.

Limits

Preemptible instances are not supported.
You must change the instance type of an ECS instance within the same instance family. The following instance families do not support instance type changes across zones:
- Heterogeneous computing instance families
- ECS Bare Metal Instance families
- Super Computing Cluster (SCC) instance families
- u1, universal instance family
- e, economy instance family
- x86-based instance families
  - Big data instance families
  - Instance families with local SSDs
  - Security-enhanced instance families
For more information about instance families, see Overview of instance families.

Migration impacts

Item	Description
Amount of time that is required to migrate an ECS instance	Approximately 15 minutes are required from the time when an instance is stopped until the time when the instance is migrated and started. Note After the computing and network resources of an ECS instance are migrated, the instance is started. After the instance is started, the system continues to migrate the disk data of the instance. In most cases, approximately 4 hours are required to migrate 100 GiB of disk data. During the migration, the I/O performance of disks degrades and you cannot perform snapshot-related and disk-related operations.
Instance status	During the migration, the ECS instance is stopped and then restarted. We recommend that you migrate the instance during off-peak hours.
Software authorization codes	After an ECS instance is migrated, its software authorization codes may change.
IP address	The public IP address of the ECS instance may change. After the instance is migrated, the system attempts to assign the original public IP address to the instance. If the original public IP address cannot be assigned to the instance, the system assigns a new public IP address to the instance. The private IP address of the ECS instance may change. After the instance is migrated, the new vSwitch assigns a new private IP address to the instance. You can modify the private IP address. For more information, see Modify the private IP address of an instance.
Number of refunds allowed	You can refund an ECS instance up to three times. An instance type downgrade may result in a refund, which consumes the refund quota.
Other	After an ECS instance is migrated, the following attributes of the instance remain unchanged: instance ID, elastic IP address (EIP), media access control (MAC) address, security groups, disk serial numbers, disk IDs, username, and logon password. If the ECS instance is added to the vServer group of a Server Load Balancer (SLB) instance before the ECS instance is migrated, the ECS instance is not automatically associated with the SLB instance after the ECS instance is migrated. You must add the ECS instance to the vServer group of the SLB instance. For more information, see the Modify a vServer group section of the "Create and manage a vServer group" topic.

Billing

When you migrate an ECS instance, if you do not change its instance type, no fee changes are involved.
Otherwise, fees are changed based on the following rules:
- If you downgrade the instance type of a subscription ECS instance, the instance type downgrade may result in a refund. The refund amount is calculated by using the following formula: Refund amount = Remaining amount of the configuration price before the downgrade - Price of the new configurations.
- If you upgrade the instance type of a subscription ECS instance, you must pay for the price difference between the original instance type and the new instance type for the remainder of the current billing cycle. Actual fees are displayed in the ECS console.
- If you change the instance type of a pay-as-you go ECS instance, you are charged based on the new instance type.

Preparations

Note

The cross-zone migration feature is commercialized, but the instance type change feature is available only to specific users. If you want to try the instance type change feature, submit a ticket. Your account will be added to the whitelist.

Create snapshots for the disks of the ECS instances to migrate. For more information, see Create a snapshot.
Make sure that the ECS instances are deployed in virtual private clouds (VPCs). If you want to change the instance type of an ECS instance that resides in the classic network, you must migrate the instance from the classic network to a VPC. For more information, see Migrate ECS instances from the classic network to a VPC.
Make sure that applications deployed on the ECS instances do not depend on the current private IP addresses of the instances. If you select a new vSwitch when you change the instance type of an ECS instance across zones, the system assigns a new private IP address to the instance.
If security software such as Safedog, Huweishen, and Yunsuo is installed on the ECS instances whose instance types you want to change, disable the software before you make cross-zone instance type changes. Otherwise, virtualization drivers may fail to be installed and the instances cannot be started. You can enable the software after the cross-zone instance type changes.
Make sure that the system disks of the ECS instances have more than 500 MiB of available space. Otherwise, virtualization drivers may fail to be installed and the instances cannot be started.
Make sure that Alibaba Cloud Global Accelerator is disabled and the following items are not configured for the instances: IPv6 addresses, high-availability virtual IP addresses (HAVIPs), elastic network interfaces (ENIs), reverse proxies, and route tables.

Procedure

Log on to the ECS console.
In the left-side navigation pane, choose Instances & Images > Instances.
In the top navigation bar, select the region and resource group to which the resource belongs.
Change the instance types of ECS instances based on your business requirements.
- To change the instance type of a single ECS instance, find the instance and choose > Network and Security Group > Migrate Instance Across Zones in the Actions column.
- To batch change the instance types of multiple ECS instances, select the instances on the Instance page and choose More > Network and Security Group > Migrate Instance Across Zones in the lower-left corner of the page.

In the Change Instance Type Across Zones dialog box, configure the parameters and click OK.

The following table describes the parameters.

Parameter	Description
Migration Task Type	The value is fixed to ECS Instance Migration.
Current Region	The region in which the ECS instances reside is displayed.
Preferred Destination Zone	Select a destination zone based on your business requirements.
Preferred Network Settings	Select a destination vSwitch. After the instances are migrated, new private IP addresses that belong to the CIDR block of the vSwitch are randomly assigned to the instances. Important After you change the instance type of an instance across zones, the original private IP address of the instance is not retained. Make sure that applications deployed on the instance do not depend on the original private IP address.
Instance Type	Specify whether to change the instance type based on your business requirements. Use Current Instance Type: Do not change the instance types. Change Instance Type: Change the instance types. For information about the instance families that support instance type changes across zones and other limits on instance type changes, see the Limits section of this topic.
Preferred New Instance Type	Select a target instance type. Note This parameter is displayed only if you select Change Instance Type.
Instance to Be Migrated	The information about the ECS instances is displayed in the Instance ID/Name, Destination Zone, Destination Instance Type, and Destination vSwitch columns.
Note	Select ECS Terms of Service and I have backed up data.

In the dialog box that appears, click Pay and complete the payment as prompted.
Go back to the ECS console to check the instance status.
A specific period of time is required to change the instance types. If the instance type of an ECS instance is changed, the status of the instance changes from Migrating to Running. You can check the progress of the cross-zone instance type change in the Server Migration Center (SMC) console. Perform the following steps:
1. Log on to the SMC console.
2. In the left-side navigation pane, click Cloud Migration > Cross-zone Migration.
3. Check the migration progress in the Real-time Migration Status column corresponding to the instance. If the instance type is changed, the status of the migration job is Completed.