Before You Start: High Availability and Reliability Requirements
The DWS service logic consists of the service layer, DWS cluster layer, OS layer, and VM layer, as shown in Table 1.
The performance of your DWS service system is impacted by these logical layers. In the event of service changes or hardware faults, you may need to make temporary adjustments or perform emergency recovery.
This section introduces cluster HA and reliability risks and suggestions in common scenarios to help you use DWS clusters better and achieve a lower recovery time objective (RTO) as a user or O&M engineer. To be specific, comply with the rules provided in Table 2 to prevent risks such as service interruptions and data loss in clusters.
| No. | Logic Layer | Description | Service Characteristic |
|---|---|---|---|
| 1 | Service layer | Applications on the service side | Service applications: gsql, JDBC, ODBC, Python, Data Studio, and Navicat |
| 2 | DWS layer | DWS clusters | Service application logic is distributed to each CN in the DWS cluster via SQL statements. Each CN then queries, optimizes, and forwards the data to DNs for processing. The DNs then aggregate the processing result and return it to the CNs, which then send it back to the application. |
| 3 | OS layer | OS installed for DWS clusters | This layer provides the foundation for running DWS, including the OS, file system, and network services. |
| 4 | VM layer | VM where DWS clusters are located | Virtual resources such as EVS disks, networks, CPUs, and memory |
| Cluster Configuration | Recommended Measure | Risk If Not Configured |
|---|---|---|
| Configuring load balancing | Use ELB to access services and distribute traffic to multiple CNs. For details, see Binding and Unbinding Load Balancers for a DWS Cluster. | When a CN is faulty, the workloads running on it cannot be automatically switched to a healthy node, causing service interruption. |
| Backing up configuration data | Use the backup function to create redundant copies of both upstream and downstream data. You are advised to perform full backup and incremental backup periodically to ensure that data can be restored to a specified point in time. | Data deleted by mistake cannot be restored, which affects your service usage and causes data security faults. |
| Configuring cluster DR | Configure cluster or service DR. For details, see DWS Cluster DR Management. | In disaster scenarios at the cluster level, it is not possible to guarantee service continuity. |
Documentation
- Introduction to CNs and DNs: Logical Cluster Architecture.
- Introduction to the ELB service: Using a Dedicated Load Balancer.
