You can create read-only instances to process massive read requests sent to the database and increase the application throughput. A read-only instance is a read-only copy of the master instance. Changes to the master instance are also automatically synchronized to all relevant read-only instances through the native replication capability of MySQL.
- Currently the following instances support read-only instances:
- MySQL 5.7 High-Availability Edition (based on local SSDs)
- MySQL 5.6
- SQL Server 2017
- Quantity of read-only instances
Database type Memory Max number of read-only instances MySQL ≥ 64 GB 10 < 64 GB 5 SQL Server Any 7
- Read-only instance is subject to an additional charge and its billing method is Pay-As-You-Go. For more information, see Pricing for read-only instances.
- The read-only instance automatically copies the whitelist its master instance, but the whitelist of the read-only instance and that of the master instance are independent. To modify the whitelist of the read-only instance, see Set a whitelist.
- Log on to the RDS console.
- Select the region where the target instance is located.
- Click the ID of the target instance to visit the Basic Information page.
- In the Instance Distribution area, click Add Read-only Instance, as shown in the following figure.
- On the purchasing page, choose the configuration of the read-only instance, and then click Buy Now.
- We recommend that the read-only instance and the master instance be in the same VPC.
- To guarantee sufficient I/O for data synchronization, we recommend that the configuration of the read-only instance (the memory) is not less than that of the master instance.
- We recommend that you purchase multiple read-only instances to improve availability.
- After creating the read-only instance, you can view it on the Instances page, as shown in the following figure.