If the zone in which the instance is located is in full load or the instance performance may be affected for other reasons, you can migrate the instance to other zones in the same region.
Note: Currently, only MySQL 5.5/5.6, SQL Server 2008 R2, PostgreSQL 9.4, PPAS 9.3 instances support instance migration across zones.
An ApsaraDB for RDS instance can be located in a single-zone or a multi-zone. A multi-zone is a physical area formed by combining multiple single zones in the same region, for example, the Multi-zone 1 (Zone B + Zone C). Compared with a single-zone instance, a multi-zone instance can withstand disasters at higher levels. For example, a single-zone instance can withstand faults at the server and rack levels, while a multi-zone instance can bear faults at the machine room 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 interface). No extra charge is collected for the use of the multi-zone.
If the zone in which the instance is located is in full load or the instance performance may be 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 have the following options for migration 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 backup database, the two databases are randomly allocated in the multi-zone. For example, when an instance having a master database and a backup database is migrated from Zone A to Multi-zone 1 (Zone B + Zone C), if the master database is allocated to Zone B, the backup database is allocated to Zone C.
Migrate the instance from a multi-zone to a single-zone. In this case, the master and backup databases of the instance are migrated to the same zone, and the level of disasters that the instance can withstand is lower.
Note: Because certain network delay occurs 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 solution. In this case, increase the overall throughput by enhancing the concurrency.
Migration across zones is possible only when the region of an instance has multiple zones.
Migration across zones is performed at the instance level, which does not change the domain name.
There is a 30 seconds of transient disconnection during migration across zones. Please make sure that your application has a reconnection policy.
Log on to RDS console.
Select the region of the target instance.
Click the target instance ID to go to the Basic Information page.
Click Migration Across Zones in the Basic Information module, as shown in the following figure.
Select a target zone on the Migrate Instance to Another Zone page and click OK, as shown in the following figure.