Creating a Read Replica

Scenarios

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

After a TaurusDB for PostgreSQL instance is created, you can create read replicas for it as needed.

Constraints

• You can only create read replicas when your account balance is not below zero.
• Up to five read replicas can be created for a DB instance.
• The specifications of a read replica must be at least equal to those of the DB instance to prevent long delay and high load. If you want the specifications of a read replica to be smaller than those of the DB instance, submit a service ticket.

Procedure

1. Log in to the TaurusDB console.
2. On the Instances page, locate the desired DB instance and click Create Read Replica in the Operation column.

   You can also enter the Create Read Replica page in either of the following ways:

   • Click the instance name to go to the Basic Information page. In the upper right corner of the page, click and choose Create Read Replica.
     Figure 1 Creating read replicas on the Basic Information page
     

   • Click the instance name to go to the Basic Information page. In the upper right corner of the page, click and choose View Instance Topology. In the instance topology, click Create Read Replica.
     Figure 2 Creating read replicas in the instance topology
     

3. Configure required parameters and click Next.
   Figure 3 Basic information
   

   Table 1 Basic information

   Parameter	Description
   Billing Mode	Pay-per-use is supported.
   Region	By default, read replicas are in the same region as your DB instance.
   DB Engine Version	Same as the DB engine of your DB instance by default and cannot be changed.
   DB Instance Type	Only Single is supported.
   AZ	You can deploy your DB instance and its read replicas in one AZ or across AZs to improve availability.
   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. Only Cloud SSD is supported. Cloud SSD: cloud disks used to decouple storage from compute.

   Figure 4 Specifications and storage
   

   Table 2 Specifications and storage

   Parameter	Description
   Instance Specifications	Refers to the vCPUs and memory of a DB instance. Different instance specifications support different numbers of database connections and maximum IOPS. For details, see TaurusDB for PostgreSQL Instance Specifications.
   CPU Architecture	Only x86 is supported. x86 instances use Intel® Xeon® Scalable processors and feature robust and stable computing performance. When working on high-performance networks, the instances provide the additional performance and stability that enterprise-class applications demand.
   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.

   Figure 5 Network and advanced settings
   

   Table 3 Network

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

   Table 4 Advanced settings

   Parameter	Description
   Enterprise Project	If your account has been associated with an enterprise project, select the target project from the Enterprise Project drop-down list. For more information about enterprise projects, see Enterprise Management User Guide.
   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 TaurusDB for PostgreSQL Tags.

4. Confirm specifications.
   • If you need to modify your settings, click Previous.
   • If you do not need to modify your settings, select the agreement and click Submit for pay-per-use read replicas.

5. 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. To view the detailed progress and result of the creation, go to the Task Center page. For details, see Task Center.

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