Creating a Read Replica

Scenarios

Read replicas enhance the read capabilities and reduce the load on your DB instances.

Constraints

By default, up to five read replicas can be created for each DB instance.

Procedure

1. Log in to the management console.
2. Click in the upper left corner of the page and choose Databases > Relational Database Service.
3. On the Instances page, locate the target DB instance and click Create Read Replica in the Operation column.

   Alternatively, click the target DB instance. In the DB instance topology, click under the primary DB instance to create read replicas.

4. On the displayed page, configure required parameters and click Next.

   Table 1 Basic information

   Parameter	Description
   Region	By default, read replicas are in the same region as your DB instance.
   DB Instance Name	Must start with a letter and consist of 4 to 64 characters. Only letters (case-sensitive), digits, hyphens (-), and underscores (_) are allowed.
   DB Engine	Same as the DB engine of your DB instance by default and cannot be changed.
   DB Engine Version	Same as the DB engine version of your DB instance by default and cannot be changed.
   Storage Type	Determines the DB instance read/write speed. The higher the maximum throughput is, the higher the DB instance read/write speed can be. Cloud SSD: cloud drives used to decouple storage from compute. The maximum throughput is 350 MB/s.
   AZ	RDS allows you to deploy your DB instance and read replicas in the same AZ.

   Table 2 Instance specifications

   Parameter	Description
   Instance Class	Refers to the vCPU and memory of a DB instance. Different instance classes have different numbers of database connections and maximum IOPS. After a DB instance is created, you can change its instance class. For details, see Changing a DB Instance Class.
   Storage Space	Contains the system overhead required for inodes, reserved blocks, and database operation. By default, storage space of a read replica is the same as that of the primary DB instance.

   Table 3 Network

   Parameter	Description
   VPC	Same as the primary DB instance's VPC.
   Subnet	Same as the primary DB instance's subnet. A floating IP address is automatically assigned when you create a read replica. You can also enter an unused floating IP address in the subnet CIDR block. After the read replica is created, you can change the floating IP address.
   Security Group	Same as the primary DB instance's security group.

   Table 4

   Parameter	Description

5. Confirm specifications.
   • If you need to modify your settings, click Previous.
   • If you do not need to modify your settings, click Submit.

6. After a read replica is created, you can view and manage it.

Follow-up Operations

Managing a Read Replica