Creating a Read Replica

Scenarios

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

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 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 your DB instance.
   DB Instance Name	Different DB instances can have the same name. The 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 the primary 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.
   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.
   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.
   Disk Encryption	Disable: indicates the encryption function is disabled. Enable: indicates the encryption function is enabled. Enabling disk encryption improves security but affects system performance. Key Name: indicates the tenant key. You can select an existing key or create a new one. NOTE: If you enable disk encryption during instance creation, the disk encryption status and the key cannot be changed later. After an RDS DB instance is created, do not disable or delete a key that is currently in use. Otherwise, RDS will be unavailable and data cannot be restored. For details about how to create a key, see the "Creating a CMK" section in the Data Encryption Workshop User Guide.

   Table 3 Network

   Parameter	Description
   VPC	Same as the primary DB instance's VPC.
   Subnet	Same as the primary instance's subnet. IPv4 address: A floating IPv4 address is automatically assigned when you create a read replica. You can also enter an unused floating IPv4 address in the subnet CIDR block. After the read replica is created, you can change the floating IP address. IPv6 address: You can create a read replica using a floating IPv6 address only when the vCPU and memory you selected support IPv6 addresses. A floating IPv6 address is automatically assigned during read replica creation and cannot be specified. After the read replica is created, the floating IP address cannot be changed.
   Security Group	Same as the primary DB instance's security group.

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 has been created, you can view and manage it on the Instances 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 name of the target read replica. You can view and manage it on the displayed page.

FAQ

Q: Does creating read replicas during peak hours increase the load on my primary instance when my primary instance's CPU usage is high?

A: Yes. When a read replica is created, it synchronizes data from the primary instance, which consumes I/O and CPU resources of the primary instance. To avoid this impact, you can create read replicas during off-peak hours.

Follow-up Operations

Managing a Read Replica