PolarDB:Add or remove a read-only node

Select different specifications for the primary node and read-only nodes

You can add read-only nodes based on your required specifications. The specifications can be different from the specifications of the primary node.

Limits

• At least one read-only node in the cluster must have the same specifications as the primary node.

• Make sure that the specifications of new read-only nodes do not differ greatly from the specifications of the primary node.

  • The memory size of a new read-only node must be at least half of the memory size of the primary node.

  • The number of CPU cores of a new read-only node must have the following mapping relationships with the number of CPU cores of the primary node.

    CPU cores of the primary node	Minimum CPU cores of a read-only node
    2	2
    4	4
    8	4
    16	8
    32	16
    64	32
    88	32

• The read-only nodes that serve as hot standby nodes must have the same specifications as the primary node.

Billing rules

Precautions

• You can add or remove read-only nodes only when the cluster does not have pending configuration changes.

• To avoid accidental operations, you can add or remove only one read-only node at a time. To add or remove multiple read-only nodes, repeat the operation multiple times.

• A read-only node can be added or removed in approximately 5 minutes. When PolarDB adds nodes to a cluster, the databases in the cluster are not affected.

• When the system removes a read-only node from a cluster, connections to the read-only node are closed. The connections to other nodes in the cluster are not affected. We recommend that you remove read-only nodes during off-peak hours and make sure that your applications can automatically reconnect to the cluster.

Add a read-only node

1. Log on to the PolarDB console.

2. In the upper-left corner of the PolarDB console, select the region in which the cluster is deployed.

3. Access the Add/Remove Node dialog box by using one of the following methods:

   • Find the cluster and choose More > Add/Remove Node in the Actions column.

   • Find the cluster and click the cluster ID. On the Basic Information page, click Add/Remove Node in the Database Nodes section.

4. Select Add Node and click OK.

   

5. Click the + icon, read and select the terms of service, and then click Buy Now.

6. On the Purchase page, confirm the order information and click Purchase.

Remove a read-only node

1. Log on to the PolarDB console.

2. In the upper-left corner of the PolarDB console, select the region in which the cluster is deployed.

3. Access the Add/Remove Node dialog box by using one of the following methods:

   • Find the cluster and choose More > Add/Remove Node in the Actions column.

   • Find the cluster and click the cluster ID. On the Basic Information page, click Add/Remove Node in the Database Nodes section.

4. Select Delete Node and click OK.

   

5. Click the - icon next to the node that you want to remove. In the dialog box that appears, click OK.

   Note

   You must retain at least one read-only node in the cluster to ensure high availability.

6. Read and select the terms of service and then click Buy Now.

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