If your workload changes periodically or you need to make planned adjustments to specifications, you can manually upgrade or downgrade the specifications (CPU and memory) of the compute nodes in a PolarDB cluster. This helps you meet performance requirements and control costs.
Assess the impact of an upgrade or downgrade
Before you manually upgrade or downgrade a cluster, you must assess the potential impact on your services and create a change plan.
Service impact
An upgrade or downgrade operation on a PolarDB cluster triggers a node restart. This causes transient disconnections and brief performance fluctuations. The impact depends on whether the cluster supports failover with hot standby and whether binary logging is enabled.
If the cluster does not support failover with hot standby, a transient disconnection of about 20 to 30 seconds may occur during the specification change. Before you perform the switch, ensure that your application has a reconnection mechanism.
If the cluster supports failover with hot standby, the specification change may cause a transient disconnection of about 5 to 10 seconds if binary logging is enabled. If binary logging is disabled, performance may drop to zero for 1 to 3 seconds, but connections and transactions will not be interrupted.
Change duration: The change task takes about 5 minutes per compute node. For example, changing two nodes takes about 10 minutes. The actual duration depends on factors such as cluster workload and the number of databases and tables.
Data latency: During the change, the data synchronization latency of read-only nodes may be higher than usual.
Data security: An upgrade or downgrade only adjusts compute node resources. It does not affect any existing data in the cluster.
Restart order: When you upgrade or downgrade the primary node and read-only nodes at the same time, the system restarts the read-only nodes first, and then restarts the primary node. No primary/standby switchover occurs during this process.
Node specification limits
To ensure cluster stability and high availability, the following limits apply to the specifications of primary and read-only nodes:
At least one read-only node must have the same specifications as the primary node.
A read-only node with hot standby enabled must have the same specifications as the primary node.
The memory of a read-only node cannot be less than half the memory of the primary node.
The minimum number of CPU cores for a read-only node is determined by the following rules:
Primary node CPU specifications
Minimum CPU specifications for read-only nodes
2
2
4
4
8
4
16
8
32
16
64
32
88
64
120
64
Multi-master Cluster (Limitless) Edition clusters are not subject to the preceding limits.
Because of their analytical workload characteristics, In-Memory Column Index (IMCI) read-only nodes should have higher specifications than the primary node.
Scope
Before you start, ensure that the following prerequisites are met.
Billing method: The target cluster must be a Subscription or Pay-as-you-go cluster.
Cluster status: The target cluster must be in the Running state, and no other configuration change tasks, such as adding nodes, deleting nodes, or performing minor version upgrades, are in progress.
Procedure
Log on to the PolarDB console. In the navigation pane on the left, click Clusters and select the region where your cluster is located.
You can navigate to the Change Configurations page in one of the following ways:
Click Change Configurations in the Actions column of the target cluster.
Click the ID of the target cluster to go to the Basic Information page. In the Database Nodes section, click Change Configurations.
In the Change Configuration dialog box, select the Upgrade or Downgrade option, and then click OK.
On the Upgrade/Downgrade page, review the Current Configuration and configure the following parameters:
Parameter
Description
Sub-series
Select the target specification series, including General Specification and Dedicated Specification.
Node
Select new specifications for the nodes to be changed. You can change the specifications for the entire cluster or set them for each node individually.
NoteMake sure that one read-only node has the same specifications as the primary node. You can configure the specifications for all other nodes as needed.
Switchover Time
Select a time to change the configurations.
Switch Now: The change task takes effect immediately.
Scheduled Switch: Select a point in time within the next 24 hours. The change task will be completed within 30 minutes after the selected time. You can view or cancel the task on the Scheduled Tasks page.
Read and agree to the Terms of Service, click Buy Now, and complete the payment. After the payment is successful, the task is executed at the scheduled switchover time.
Billing
Upgrading or downgrading a cluster affects the billing. The rules vary depending on the cluster's billing method.
Pay-as-you-go: After a successful upgrade or downgrade, you are charged hourly based on the price of the new specifications.
Subscription:
Upgrade: You must pay the price difference between the new and old specifications for the remaining subscription period.
Downgrade: The system automatically calculates the remaining value and issues a refund. For more information, see Refund amount calculation.
Related API operations
API | Description |
Changes the specifications of a PolarDB cluster node. | |
Changes the specifications of a single node in a PolarDB cluster. |