Creating a Read Replica

Scenarios

Read replicas are used to enhance the read capabilities of primary DB instances and reduce the load on primary DB instances.

Procedure

1. Log in to the management console.
2. Click in the upper left corner and select a region and a project.
3. Click Service List. Under Database, click Relational Database Service. The RDS console is displayed.
4. On the Instance Management 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.

5. On the displayed page, configure information about the DB instance and click Next.

   Table 1 Basic information

   Parameter	Description
   Region	By default, read replicas are in the same region as the primary DB instance.
   DB Instance Name	Must start with a letter and consist of 4 to 64 characters. It can contain only uppercase letters, lowercase letters, digits, hyphens (-), and underscores (_).
   DB Engine	Same as the DB engine version of the primary DB instance by default and cannot be changed.
   DB Engine Version	Same as the DB engine version of the primary DB instance by default and cannot be changed.
   AZ	RDS allows you to deploy primary DB instances and read replicas in a single AZ or across AZs. You can determine whether the read replica AZ is the same as the primary AZ. If they are the same, the read replica and primary DB instance are deployed in the same AZ. If they are different, the read replica and primary DB instance are deployed in different AZs to ensure data reliability.

   Table 2 Instance specifications

   Parameter	Description
   Instance Class	Refers to the CPU and memory of a DB instance. Different instance classes refer to different numbers of database connections and maximum IOPS.
   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. Common I/O: uses the SATA disk type that supports a maximum throughput of 90 MB/s. Ultra-high I/O: supports a maximum throughput of 350 MB/s.
   Storage Space	Contains the system overhead required for inode, reserved block, 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 VPC.

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

7. After a read replica has been created, you can view and manage it on the Instance Management page by clicking on the left of the DB instance to which it belongs.

   Alternatively, click the target DB instance. In the DB instance topology, click the target read replica. You can view and manage it in the displayed pane.

Follow-up Operations

Managing a Read Replica