When Should I Add CNs or Scale out a cluster?
Introduction to CN Concurrency
CN is short for Coordinator Node. A CN is an important component of GaussDB(DWS) and is closely related to users. It provides interfaces to external applications, optimizes global execution plans, distributes execution plans to DataNodes, and summarizes and processes execution results. A CN is an interface to external applications. The concurrency capability of the CN determines the service concurrency.
CN concurrency is determined by the following parameters:
- max_connections: specifies the maximum number of concurrent connections to the database. This parameter affects the concurrent processing capability of the cluster. The default value depends on the cluster specifications. For details, see Managing Database Connections.
- max_active_statements: specifies the maximum number of concurrent jobs. This parameter applies to all the jobs on one CN. The default value is 60, which indicates a maximum of 60 jobs can run at the same time. Other jobs will be queued.
Add CNs or Scale out a Cluster?
- Insufficient connections: When a cluster is created for the first time, the default number of CNs in the cluster is 3, which can meet the customer's basic connection requirements. If the cluster has a large number of concurrent requests and the number of connections to each CN is large, or the CPU usage of a CN exceeds its capacity, you are advised to add CNs. For details, see CNs.
- Insufficient storage capacity and performance: If your business grows and you have higher requirements on storage capacity and performance, or the CPU of your cluster is insufficient, you are advised to scale out your cluster. For details, see Scaling Out a Cluster.
With the expansion of cluster nodes, more CNs are needed to meet the distribution requirements of GaussDB(DWS). In short, adding CNs does not necessarily require cluster scale-out. However, after cluster scale-out, CNs may need to be added.
Cluster Management FAQs
- What Do I Do If Creating a GaussDB(DWS) Cluster Failed?
- How Can I Clear and Reclaim the Storage Space?
- Can I Switch My Cluster Nodes to Another Region After Purchase?
- Why Did the Used Storage Shrink After Scale-out?
- How Do I View Node Metrics (CPU, Memory, and Disk Usage)?
- Does GaussDB(DWS) Support a Single Node for a Learning Environment?
- Does GaussDB(DWS) Support BMS?
- How Is the Disk Space or Capacity of GaussDB(DWS) Calculated?
- What Are the gaussdb and postgres Databases of GaussDB(DWS)?
- How Do I Set the Maximum Number of Sessions When Adding an Alarm Rule on Cloud Eye?
- How Do I Determine Whether a Cluster Uses the x86 or Arm Architecture?
- What Should I Do If the Scale-out Check Fails?
- When Should I Add CNs or Scale out a cluster?
- What Are the Scenarios of Resizing a Cluster, Changing the Node Flavor, Scale-out, and Scale-in?
- How Should I Select from a Small-Flavor Many-Node Cluster and a Large-Flavor Three-Node Cluster with Same CPU Cores and Memory?
- What Are the Differences Between Cloud SSDs and Local SSDs?
- What Are the Differences Between Hot Data Storage and Cold Data Storage?
- What Do I do if the Scale-in Button Is Dimmed?
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