doc-exports/docs/rds/umn/en-us_topic_add_read_replica.html

Creating a Read Replica

Scenarios

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

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

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 Instances page, locate the target DB instance and choose More > Create Read Replica in the Operation column.
5. On the displayed page, configure required parameters and click Create Now.

   Table 1 Basic Settings

   Parameter	Description
   Region	By default, read replicas are in the same region as the primary DB instance.

   Table 2 Engine Options

   Parameter	Description
   DB Engine	Same as the DB engine 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.
   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. Extreme SSD: uses 25GE network and RDMA technologies to provide you with up to 1,000 MB/s throughput per disk and sub-millisecond latency. Flexible SSD: decouples capacity from performance and allows for tailored IOPS and throughput for your business requirements. This storage type is ideal for mainstream interactive applications that require high performance and low latency.
   AZ	RDS allows you to deploy primary DB instances and read replicas in a single AZ or across AZs to improve reliability.

   Table 3 Instance Configuration

   Parameter	Description
   Instance Class	Refers to the CPU and memory of a DB instance. Different instance classes have different numbers of database connections and maximum IOPS. For details about instance classes, see section DB Instance Classes. After a DB instance is created, you can change its instance class (CPU and memory). For details, see section Changing a DB Instance Class.
   Storage Space	Contains the file 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.
   IOPS	This parameter is required when the storage type is Flexible SSD. The value range is from 3000 to 128000. The IOPS is limited by the disk size and must be no greater than 500 times the disk capacity.
   Throughput	This parameter is required when the storage type is Flexible SSD. The value ranges from 125 to 1000 (in MiB/s) and must also be no greater than the IOPS divided by 4.
   Disk Encryption	Enabling disk encryption enhances data security but reduces the database's read and write performance by 5%. Key Name: indicates the tenant key. Select one from the drop-down list. After disk encryption is enabled, the following restrictions apply: If you enable disk encryption during instance creation, the disk encryption status and the key cannot be changed later. Enabling disk encryption will not encrypt backup data stored in Object Storage Service (OBS). Keep the key secure. Once the key is disabled, deleted, or frozen, your instance will be inaccessible and its data may not be restored.

   Table 4 Basic Settings

   Parameter	Description
   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 (_).

   Table 5 Connectivity

   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.

   Table 6 Additional Options

   Parameter	Description
   Tag	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 20 tags can be added for each DB instance. After a DB instance is created, you can click it and view its details on the Tags page. For details, see section Managing 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 is created, you can view and manage it.

   For details about how to manage read replicas, see Managing a Read Replica.

   You can view the detailed progress and result of the task on the Task Center page.

Follow-up Operations

Managing a Read Replica

Parent topic: Read Replicas