• Relational Database Service

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  2. Relational Database Service
  3. User Guide
  4. Getting Started with MySQL
  5. Creating Read Replicas
  6. Creating a Read Replica

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.

After DB instances are created, you can create read replicas for them.

NOTE:

A maximum of five read replicas can be created for a primary DB instance.

Procedure

  1. On the Instance Management page, locate the target DB instance and choose More > Create Read Replica in the Operation column.
  2. On the displayed page, configure information about the read replica and click Create Now.

    Table 1 Basic information

    Parameter

    Description

    AZ

    RDS allows you to deploy both a primary DB instance and a read replica in a single AZ or across AZs.
    • 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.

    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.

    Disk Encryption

    • Disabled: indicates the encryption function is disabled.
    • Enabled: indicates the encryption function is enabled, improving data security but affecting system performance.

      Key Name: indicates the tenant key. You can create or select a key.

      NOTE:
      • Once the disk encryption function is enabled, you cannot disable it or change the key after a DB instance is created. Backup data will not be encrypted in OBS.
      • After an RDS DB instance is created, do not disable or delete the key that is being used. 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 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.

    For details about instance classes, see section DB Instance Specifications.

    After a DB instance is created, you can change its CPU and memory. For details, see section Changing the CPU or Memory of a DB Instance.

    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: uses the SSD disk type that supports a maximum throughput of 350 MB/s.

    Storage Space

    Contains the system overhead required for inode, reserved block, and database operation.

    • Can range in size from 40 GB to 4,000 GB and can be scaled up only by a multiple of 10 GB.
    • The storage space of the read replica must be greater than or equal to that of the primary instance.
    Table 3 Tags

    Parameter

    Description

    Tags

    Tags an RDS DB instance. This configuration is optional. Adding tags to RDS DB instances helps you better identify and manage the DB instances. A maximum of 10 tags can be added for each DB instance.

    After a DB instance is created, you can view its tag details on the Tags tab. For details, see section Tags.

  3. Confirm the DB instance specifications.

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

  4. 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.