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 and select a region and a project.
3. Click in the upper left corner of the page and choose Database > Relational Database Service.
4. On the Instances page, locate the target DB instance and click Create Read Replica in the Operation column.
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 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. Ultra-high I/O: supports a maximum throughput of 350 MB/s.
   AZ	RDS allows you to deploy your DB instance and read replicas in a single AZ or across AZs to improve reliability.

   Table 2 Specifications and storage

   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. For details about instance classes, see RDS for SQL Server Instance Classes. After a DB instance is created, you can change its vCPU and memory. 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.
   Disk Encryption	Disable: Encryption is disabled. Enable: Encryption is enabled, which improves data 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 the 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. For details about how to create a key, see the "Creating a CMK" section in the Key Management Service 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.
   Security Group	Same as the primary DB instance's security group.

   Table 4 Tags

   Parameter	Description
   Tag	Optional. Tags help you easily identify and manage your read replicas. A maximum of 20 tags can be added for each read replica. After a read replica is created, you can view its tag details on the Tags page. For details, see RDS for SQL Server Tags.

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 Instances page by clicking on the left of the DB instance to which it belongs.

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