This topic describes the hot standby storage cluster feature of PolarDB for MySQL.
Introduction
PolarDB for MySQL provides the hot standby storage cluster feature. A hot standby storage cluster is deployed in the secondary zone or a different data center in the same zone of the region where a PolarDB cluster is deployed. The hot standby storage cluster uses independent storage and compute resources. When the PolarDB cluster or the primary zone becomes unavailable, the hot standby storage cluster is quickly promoted to primary to handle read and write requests.
Hot standby storage cluster solutions
PolarDB for MySQL supports the following hot standby storage cluster solutions:
Disabling the hot standby storage cluster feature
Overview
Database services are only provided by the cluster in the primary zone. This solution is less costly.
However, it takes longer time to recover services in case the primary zone fails. If you require cross-zone high availability, we recommend that you enable the hot standby storage cluster feature.
Scenarios
Website and application development: You can offload routine database O&M tasks and focus on your own business.
Personal learning: You can use the standard PolarDB service for learning databases and testing.
R&D and testing: Expedited delivery enables flexible scaling of database services according to your needs, significantly improving R&D and testing efficiency.
Enabling the hot standby storage cluster feature
Only PolarDB for MySQL Enterprise Edition supports this feature.
Overview
Data is distributed in multiple zones. The primary zone and secondary zone each keep a copy of data, which ensures the delivery of services outlined in the service level agreement (SLA).
All compute nodes are required to be deployed in the primary zone. In the event of primary zone failures, database services are switched over to the hot standby storage cluster.
The following figure shows the topology on the Basic Information page of a PolarDB cluster after the hot standby storage cluster feature is enabled.
Scenarios
The classic high-availability architecture is suitable for more than 80% of use cases in various industries, such as Internet, IoT, online retailing, logistics, and gaming.
Billing
If the hot standby storage cluster feature is disabled, only the primary cluster is deployed to store three replicas. The unit price in this case is half of that when the hot standby storage cluster feature is enabled.
Procedures: Enable the hot standby storage cluster
You can choose to enable or disable the feature at cluster creation. If you choose to disable the feature, you can enable it for your cluster afterwards.
This section describes how to enable the hot standby storage cluster feature for a PolarDB Enterprise Edition cluster.
If you choose to enable this feature at cluster creation, you cannot disable it for your cluster afterwards.
Log on to the PolarDB console.
Go to the Basic Information page of the cluster.
In the Distributed Storage section at the bottom of the page, click Enable Hot Standby Storage Cluster.
On the page that appears, select Enable Hot Standby Storage Cluster, read and select the terms of service, and then click Buy Now.
The feature is enabled after a while.
