Adjusting the Number of Local Disk Nodes
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In the architecture of a TencentDB for MySQL instance, adding a replica node provides an additional data copy. Compared to a single-node deployment, two-node, three-node, and four-node architectures offer higher availability and greater disaster recovery capabilities. This document describes how to scale the number of nodes up or down for a TencentDB for MySQL instance with local disks.
Scenarios
Note:
Increasing or decreasing the number of replica nodes upgrades or downgrades the instance architecture. For example, adding one replica node to a two-node architecture upgrades it to a three-node architecture.
A two-node (local disk) instance is upgraded to a three-node (local disk) instance.
A two-node (local disk) instance is upgraded to a four-node (local disk) instance.
A three-node (local disk) instance is upgraded to a four-node (local disk) instance.
A three-node (local disk) instance is downgraded to a two-node (local disk) instance.
A four-node (local disk) instance is downgraded to a three-node (local disk) instance.
A four-node (local disk) instance is downgraded to a two-node (local disk) instance.
Feature Limits
Two-node economical instances do not support upgrades to three-node (local disk) instances/four-node (local disk) instances.
Three-node (local disk) instances/four-node (local disk) instances do not support downgrades to two-node economical instances.
Feature Overview
Adding replica nodes does not affect the normal use of the instance. During the upgrade, your business can be accessed normally.
After you remove replica nodes, the data remains on the original nodes but no longer participates in synchronization. Reducing the number of nodes decreases the high availability of the instance. Proceed with caution.
In addition to directly adjusting the architecture of an existing instance, you can also directly create an instance with the target architecture on the purchase page.
When tables without primary keys exist, data migration may take longer.
Operation Steps
1. Log in to the TencentDB for MySQL console.
2. In the instance list, locate the target instance, and click Instance ID or Manage in the Operation column to go to the instance details page.
3. Choose Instance Details > Specification Configurations, and click Adjust Nodes next to Architecture.
4. In the pop-up window, complete the following configurations as needed, and click OK.
Parameter | Description |
Current Instance Configuration | This item displays the configuration information of the current instance, showing the instance architecture before node changes. |
Target Node Configuration | Adjusting node configurations as needed Add Standby Node: This operation increases the number of replica nodes. For a two-node instance, you can add 1 to 2 replica nodes, which upgrades the instance to a three-node/four-node architecture accordingly. For a three-node instance, you can add 1 replica node, which upgrades the instance to a four-node architecture. After adding replica nodes, you can select the AZ for the replica nodes. You can choose an AZ that is the same as or different from that of other nodes. The specific range of available AZs is subject to the actual configuration page. Delete: This operation reduces the number of replica nodes. For a three-node instance, you can remove 1 replica node, which downgrades the instance to a two-node architecture. For a four-node instance, you can remove 1 to 2 replica nodes, which downgrades the instance to a three-node/two-node architecture accordingly. |
Estimated Impact | The system provides an estimated impact prompt based on the node configuration you selected. You need to focus on reading this prompt. |
Data Replication Mode | Select a data replication mode between the primary and secondary nodes. Options include: strong sync replication (not supported for dual-node architecture), semi-sync replication, and async replication. For an introduction to data replication modes, see Database Instance Replication. Note: When you select strong sync replication or semi-sync replication as the data replication mode, you need to set the number of synchronous wait nodes. When you select async replication as the data replication mode, you do not need to set the number of synchronous wait nodes. |
Strong Sync Waiting Node | This item is configurable when the data replication mode is set to strong sync replication. In strong sync replication mode, after the primary node executes a transaction, you need to select the minimum number of nodes that must return an ACK (acknowledging receipt of the binlog) for the transaction to be considered successfully committed. For three-node/four-node architectures, the options are: 1 node or 2 nodes. Note: For core services (such as payment/transaction), we recommend that you select two nodes to improve data reliability. For non-core services, selecting one node is recommended for better performance. |
Synchronous Wait Node | This item is configurable when the data replication mode is set to semi-sync replication. In semi-sync replication mode, after the primary node executes a transaction, you need to select the minimum number of nodes that must return an ACK (acknowledging receipt of the binlog) for the transaction to be considered successfully committed. For three-node/four-node architectures, the options are: 1 node or 2 nodes; for dual-node architecture, the option is: 1 node. Note: For core services (such as payment/transaction), we recommend that you select two nodes to improve data reliability. For non-core services, selecting one node is recommended for better performance. |
5. After the payment is completed, you are returned to the instance list. The instance status is Configuration Adjustment. After the status changes to Running, the configuration adjustment is completed.
FAQs
How to View Instance Architecture?
You can log in to the MySQL console, view the architecture information at Configuration in the instance list, or click Instance ID or Manage in the Operation column to go to the instance details page, and view the architecture information at Architecture under Specification Configurations.
How to View the AZs of the Primary and Secondary Databases of an Instance?
You can log in to the MySQL console, in the instance list, click Instance ID or Manage in the Operation column to go to the instance details page, and view the primary and secondary AZs in Instance Info > AZ.
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