PolarDB allows you to create a PolarDB for MySQL cluster by migrating an ApsaraDB RDS for MySQL instance. The created PolarDB cluster uses the accounts, databases, IP address whitelist, and required parameters of the source ApsaraDB RDS for MySQL instance.
Benefits
- The endpoint of the source database is retained. You can switch to PolarDB without changing the connection settings of your applications.
- You can complete data migration in the PolarDB console. No data migration tools such as Data Transmission Service (DTS) are required.
- The data migration feature is free of charge to use.
- No data loss occurs during the migration.
- Incremental data migration is supported. This allows you to migrate data with a service downtime of less than 10 minutes.
- Hot migration is supported. Only a single transient disconnection occurs during the data migration from ApsaraDB RDS for MySQL to PolarDB.
- Migration rollbacks are supported. If a migration fails, the migration can be rolled back within 10 minutes.
Prerequisites
- The edition of the source RDS instance is ApsaraDB RDS for MySQL 5.6 or 5.7 High-availability Edition, and the storage type is local SSD.
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- For ApsaraDB RDS for MySQL 5.6, the minor version of the kernel must be 20190815 or later.
- For ApsaraDB RDS for MySQL 5.7, the minor version of the kernel must be 20200331 or later.
Note You can run theshow variables like '%rds_release_date%';
command to view the minor version of the kernel for the source RDS instance. If the minor version of the kernel for the source RDS instance is earlier than the preceding version, you can upgrade the minor version of the kernel to the latest version. For more information, see Update the minor engine version of an ApsaraDB RDS for MySQL instance. - Transparent Data Encryption (TDE) and SSL are disabled on the source RDS instance. For more information, see TDE and SSL.
- The table storage engine for the source RDS instance is InnoDB.
- If Database Proxy (Safe Mode) is enabled for the RDS instance, a privileged account
is created or the network connection mode of the RDS instance is switched to high-performance
mode. For more information, see Create an account and [Important] RDS network link upgrade.
Switching with endpoints
When you perform data migration from ApsaraDB RDS for MySQL to PolarDB, you can select Switch with Endpoints (Connection Changes Not Required). Then, the system interchanges the endpoints between the RDS instance and the PolarDB cluster. In this case, you do not need to modify the configurations of your applications to connect to the PolarDB cluster. The following figure shows the rules for endpoint interchanges between the RDS instance and the PolarDB cluster.

To switch with endpoints, take note of the following limits:
- Only the endpoints of the RDS instance and the PolarDB cluster are interchanged. The other configurations such as the vSwitches and virtual IP addresses remain the same as before.
- Endpoints can be interchanged only if both the source RDS instance and the destination PolarDB cluster have endpoints. By default, only the primary endpoints in the internal network can be interchanged.
- If you want to switch to a different endpoint, you must create these endpoints before the switchover. For more information about how to create endpoints for the PolarDB cluster, see Configure the PolarDB proxy. For more information about how to create endpoints for the RDS instance, see Configure endpoints for an RDS instance.
- The port numbers are not interchanged between the RDS instance and the PolarDB cluster. You must make sure that the port number of the RDS instance is the same as that of the PolarDB cluster. The default port number used by RDS and PolarDB is 3306. If the port numbers are different, change one of the port numbers. For more information, see View and change the internal and public endpoints and port numbers of an ApsaraDB RDS for MySQL instance and Modify or delete an endpoint.
- After the endpoints are interchanged, issues may occur due to the expiration of the Domain Name System (DNS) cache data. The databases in the PolarDB cluster may fail to be connected or support only read operations. We recommend that you refresh the DNS cache data of your server to fix this issue.
- If you want to use Data Management (DMS) to log on to the PolarDB database after the endpoints are interchanged, you must use the latest version of DMS and the cluster ID to log on to the database. You cannot log on to the database by using the endpoint.
Limits
- Cross-region data migration is not supported.
- You cannot set the parameters of the source RDS instance during data migration.
Pricing
You are not charged for data migration from the source RDS instance to the PolarDB cluster. You are charged only for the purchased PolarDB cluster. For more information, see Billable items.
Procedure
Step | Description |
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1. Migrate data from the source RDS instance | In this step, a PolarDB cluster is created. The cluster stores the same data as the source RDS instance. Then, incremental data is synchronized from the source RDS instance to the PolarDB cluster in real time. |
2. Switch over services |
Note If data errors occur after the switchover is complete, you can roll back the migration.
This allows you to restore the database and data to the state before the data migration.
For more information, see Roll back the migration.
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3. Complete the migration |
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Step 1: Migrate data from the source RDS instance
In this step, a PolarDB cluster is created. The cluster stores the same data as the source RDS instance. Then, incremental data is synchronized from the source RDS instance to the PolarDB cluster in real time.
Step 2: Switch over services
Step 3: Complete the migration
Roll back the migration (optional)
If data errors occur before the migration is complete, you can roll back the migration. This allows you to restore the database and data to the state before the data migration. After the rollback, the read/write state of the source RDS instance is changed to Read and Write, and the read/write state of the PolarDB cluster is changed to Read Only. The system synchronizes data from the RDS instance to the PolarDB cluster.
FAQ
- What are the differences among creating a PolarDB for MySQL cluster by migrating an
ApsaraDB RDS for MySQL instance, creating an PolarDB for MySQL cluster by using the Clone from RDS method (Create a ApsaraDB PolarDB MySQL-compatible edition cluster by cloning an ApsaraDB RDS for MySQL instance), and migrating data from an ApsaraDB RDS for MySQL instance to a PolarDB for MySQL cluster (Migrate data from an ApsaraDB RDS for MySQL instance to a PolarDB for MySQL cluster)?
The following table describes the differences.
Item Create a PolarDB for MySQL cluster by migrating an ApsaraDB RDS for MySQL instance Create a ApsaraDB PolarDB MySQL-compatible edition cluster by cloning an ApsaraDB RDS for MySQL instance Migrate data from an ApsaraDB RDS for MySQL instance to a PolarDB for MySQL cluster Whether DTS is required No No Yes Whether incremental data migration or synchronization is supported Yes No Yes Whether operations on the source RDS instance are affected No No No Whether the source and destination databases can use different MySQL versions No No Yes Note - Do the node specifications of PolarDB for MySQL need to be the same as those of the source ApsaraDB RDS for MySQL instance?
You can select the specifications of PolarDB for MySQL based on your business requirements. We recommend that you select specifications that are the same as or more advanced than those of the source RDS instance. All nodes in the PolarDB Cluster Edition cluster are dedicated nodes. The dedicated nodes provide stable and reliable performance. For more information, see Billable items.
- Do I need to purchase a PolarDB for MySQL cluster before the upgrade from RDS to PolarDB?
You do not need to purchase a PolarDB for MySQL cluster in advance. You can perform the operations that are described in Step 1: Migrate data from the source RDS instance to purchase and create a PolarDB cluster that has the same data as the source RDS instance.
- Is the source RDS instance affected when data is migrated from the RDS instance?
No, the source RDS instance is not affected when data is migrated from the RDS instance.
- What are the impacts of smooth migration on the RDS instance?
The migration does not affect the operations on the source RDS instance. However, data migration involves read operations, and read operations affect query performance on the source RDS instance.
- What are the impacts of smooth migration on my workloads that run on the databases?
A smooth migration ensures that no data is lost during the migration. The service downtime is less than 10 minutes. During service downtime, the service is suspended and does not generate incremental data but the database is not stopped. You can roll back the migration based on your business requirements.
- What happens if I cancel the migration?
After the migration is canceled, you can modify the parameters of the source RDS instance. The read/write state of the PolarDB cluster is changed to Read and Write, and the data in the cluster is not deleted. If you manually cancel the migration, you can specify whether to disable the binary logging feature for the PolarDB cluster. Binary logging is not disabled if the migration is automatically canceled.
- Do I need to change the endpoint in my applications after the service is switched
over to PolarDB?
When you switch over services, you can select Switch with Endpoints (Connection Changes Not Required). Then, the system interchanges the endpoints between the RDS instance and the PolarDB cluster. In this case, you do not need to modify the configurations of your applications to connect to the PolarDB cluster.
- I select Switch with Endpoints (Connection Changes Not Required) when I switch over services. Why do I need to use the new endpoint to connect to the PolarDB cluster?
Endpoints can be interchanged only if both the source RDS instance and the destination PolarDB cluster have endpoints. By default, only the primary endpoint in the internal network is interchanged. If you want to switch to a different endpoint, you must create these endpoints before the switchover. For more information about how to create endpoints for the PolarDB cluster, see Apply for a cluster endpoint or a primary endpoint. For more information about how to create endpoints for the RDS instance, see Configure endpoints for an RDS instance.
- If the source RDS instance contains read-only instances, can the endpoints of read-only
instances be switched when Switch with Endpoints (Connection Changes Not Required) is selected?
No, the endpoints of read-only instances cannot be switched. The endpoints of the source RDS read-only instances are not migrated when you upgrade from RDS to PolarDB. Only the endpoints and read/write splitting endpoints of the source RDS primary instance are migrated. You must manually modify the endpoints of the source RDS read-only instances in your applications to the endpoints of the PolarDB cluster.
- After the switchover, connections to the PolarDB databases cannot be made or data cannot be written to the databases. Why?
After the endpoints are interchanged, issues may occur due to the expiration of the DNS cache data. The databases in the PolarDB cluster may fail to be connected or support only read operations. We recommend that you refresh the DNS cache to fix this issue.
- Can I perform a compatibility test and evaluate the workloads before the migration
to the PolarDB cluster?
You can first perform the operations described in Create a ApsaraDB PolarDB MySQL-compatible edition cluster by cloning an ApsaraDB RDS for MySQL instance to clone data to the PolarDB cluster for compatibility tests and workload evaluation. Then perform the operations in this topic to upgrade to PolarDB.
- Why does the Complete Migration button not appear in the PolarDB console after I switch over services?
If you complete the Complete Migration step, this button disappears. This avoids repeated operations.
- After the upgrade to PolarDB, do I need to create the same username and password in the PolarDB cluster as those in the source RDS instance?
No, you do not need to create the same username and password in the PolarDB cluster. The created PolarDB cluster retains the accounts, databases, IP address whitelist, and required parameters of the source ApsaraDB RDS for MySQL instance.
- How do I perform migration from a source RDS instance that has TDE or SSL enabled
to the PolarDB cluster?
RDS instances that have TDE or SSL enabled cannot be upgraded to PolarDB clusters. You can use DTS to migrate data from the source RDS instance to the PolarDB cluster. For more information, see Migrate data from an ApsaraDB RDS for MySQL instance to a PolarDB for MySQL cluster.
- Can I perform a cross-version upgrade when I create a PolarDB cluster by migrating an ApsaraDB RDS for MySQL instance? For example, can I upgrade
from ApsaraDB RDS for MySQL 5.6 to PolarDB for MySQL 8.0?
No, you cannot perform a cross-version upgrade. To upgrade ApsaraDB RDS for MySQL 5.6 to PolarDB for MySQL8.0, you must use DTS to migrate data. For more information, see Migrate data from an ApsaraDB RDS for MySQL instance to a PolarDB for MySQL cluster.
- If a DTS data synchronization task is started for the source RDS instance before the
upgrade to PolarDB for MySQL, is the task affected during the upgrade?
No, when you perform operations described in this topic, full data is first cloned from the source RDS instance to the new PolarDB cluster. Then, incremental data is synchronized from the source RDS instance to the PolarDB cluster in real time. The data source of the DTS task is still the source RDS instance. The data migration to the PolarDB cluster does not affect the operations on the source RDS instance.
However, after the data is migrated, if you switch your services to the new PolarDB cluster and the source RDS instance is no longer used, the data source of DTS is not automatically changed to the new PolarDB cluster. In this case, you must create a DTS synchronization task and change the data source to the PolarDB cluster.
References
API operation | Description |
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CreateDBCluster | Creates a PolarDB cluster.
Note If you create a PolarDB cluster by migrating an ApsaraDB RDS for MySQL instance, set CreationOption to MigrationFromRDS.
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DescribeDBClusterMigration | Queries the migration state of a specified PolarDB cluster. |
ModifyDBClusterMigration | Switches or rolls back the task that migrates data from RDS to PolarDB. |
CloseDBClusterMigration | Cancels or completes the migration for a PolarDB cluster. |