If the zone in which the instance is located is in full load or the instance performance is affected for other reasons, you can migrate the instance to other zones in the same region. During the migration, the RDS service is interrupted and certain operations cannot be performed. Therefore, we recommend that you set the migration time to off-peak hours. This document describes migration details.

Note
Currently, only MySQL 5.5/5.6, SQL Server 2008 R2, PostgreSQL 9.4, PPAS 9.3 instances support instance migration across zones.

Background information

You can select between single-zone and multi-zone instances. A multi-zone is a physical area created through combination of multiple single zones in the same region. For example, you can create multi-zone 1 by combining zone B and zone C. Compared to single-zone instances, multi-zone instances can withstand high-level disasters. For example, single-zone instances can withstand faults at the server and rack level, while multi-zone instances can withstand faults at the data center level.

Currently, multi-zones are supported in China East 1 (Hangzhou), China East 2 (Shanghai), China North 2 (Beijing), China South 1 (Shenzhen), Hong Kong, and Singapore (the regions supporting multi-zones may be updated. Select one of the available options on the RDS console). No extra fee is charged for the use of a multi-zone.

If the zone in which the instance is located is in full load or the instance performance is affected for other reasons, you can migrate the instance to other zones in the same region. Instance migration across zones involves copying the instance data to the new zone, and the migration is performed at the instance level. After the instance is migrated to a new zone, all its attributes and configurations remain the same. It often takes several hours to migrate an instance to a new zone, and the time is subject to the instance size. After all the instance data is copied to the new zone, the instance is deleted from the original zone.

You can choose one of the following methods to migrate an instance across zones:

  • Migrate the instance from a single zone to another single zone.
  • Migrate the instance from a single zone to a multi-zone. In this case, if the instance has a master database and a slave database, the two databases are randomly allocated in the multi-zone. For example, when an instance with a master database and a slave database is migrated from zone A to multi-zone 1 (zone B + zone C), if the master database is allocated to zone B, the slave database is allocated to zone C.
  • Migrate the instance from a multi-zone to a single zone. In this case, the master and slave databases of the instance are migrated to the same zone, and the instance can withstand lower-level disasters.
Note
Because certain network delay exists between multi-zones, the response time of a multi-zone instance to a single update may be longer than that of a single-zone instance when a multi-zone instance adopts the semi-synchronous data replication mode. In this case, increase the overall throughput by enhancing the concurrency.

Attentions

  • Migration across zones is possible only when the region of an instance has multiple zones.
  • During the migration across zones, most management operations cannot be performed. Therefore, choose an appropriate time for the migration. The following lists the operations that can or cannot be performed:
    Operation Whether the operation can be performed
    Modify the whitelist Yes
    Enable SQL audit Yes
    Set the maintenance period Yes
    Add read-only instances No
    Add disaster recovery instances No
    Release an instance No
    Change the billing method to the Subscription mode No
    Change configurations No
    Create a common or master account No
    Reset the account password No
    Modify account permissions No
    Create and delete databases No
    Change the network type No
    Change the access mode No
    Modify the connection address No
    Apply for an Internet IP address No
    Switch between master and slave databases No
    Change the data backup mode No
    Restore instance data No
    Modify parameters No
  • There is a 30 seconds of transient disconnection during migration across zones. Make sure that your application has a reconnection policy.

Procedure

  1. Log on to the RDS console.
  2. Select the region of the target instance.
  3. Click the target instance ID to go to the Basic Information page.
  4. Click Migration Across Zones in the Basic Information area, as shown in the following figure.


  5. Select a target zone in the Migrate Instance to Other Availability Zones dialog box, as shown in the following figure.


    Parameter description:

    • Migrate to: Select the region to which you want to migrate the instance.
    • Switching Time: Choose when to perform the migration. During the migration, many operations cannot be performed. You can choose to switch immediately or at a later time.
  6. To modify the maintenance time, perform the following steps. Alternatively, you can also leave the maintenance time unchanged.
    1. Click Modify, as shown in the following figure. The Basic Information page is displayed.


    2. At the lower left corner, select a maintenance period in the Configuration Information area and click Save.


    3. Go back to the page for migrating the instance to another zone.
  7. In the Migrate Instance to Other Availability Zones dialog box, click OK.