RDS for MySQL Primary/Standby Instances

This section describes the architecture, advantages, and scenarios of RDS for MySQL primary/standby instances.

Introduction

A primary/standby instance uses an HA architecture and can be deployed across AZs. The primary and standby instances share the same IP address.

When a primary instance is being created, a standby instance is provisioned synchronously to provide data redundancy. The standby instance is invisible to you after being created.
If the primary instance fails, a failover occurs, during which database connection is interrupted. If there is a replication delay between the primary and standby instances, the failover takes an extended period of time. The client needs to be able to reconnect to the instance.

Table 1 lists the technical specifications supported by each RDS for MySQL series.

Advantages

The standby node of a primary/standby DB instance is only used for failover and restoration. It does not provide services. The performance of single-node DB instances is similar to or even higher than primary/standby DB instances because standby nodes cause extra performance overhead.

Scenarios

Production databases of large and medium enterprises
Applications for the Internet, Internet of Things (IoT), retail e-commerce sales, logistics, gaming, and other industries

Function Comparison

**Table 1** Comparison of basic functions
Item	Single-Node	Primary/Standby
Number of nodes	1	2 (default) By default, a primary/standby instance consists of two nodes (one primary and one standby). You can create read replicas if needed.
Standby node readable	N/A	No
Address type	Read/write address	Read/write address
Primary/standby replication mode	N/A	Asynchronous and semi-synchronous
Maximum number of tolerable faulty nodes	0	1
Multi-AZ DR	N/A	Supported
Specifications	vCPUs: a maximum of 128 Memory: a maximum of 1,024 GB Storage: a maximum of 4,000 GB Final specifications on the console may differ slightly.	vCPUs: a maximum of 128 Memory: a maximum of 1,024 GB Storage: a maximum of 4,000 GB Final specifications on the console may differ slightly.
Monitoring and alarms	Supported	Supported
Security group	Supported	Supported
Backup and restoration	Supported	Supported
Parameter settings	Supported	Supported
SSL	Supported	Supported
Log management	Supported	Supported
Read replicas (which need to be created)	Supported	Supported
Read/write splitting	Supported	Supported
SQL audit	Supported	Supported
DBA Assistant	Supported	Supported
Monitoring by Seconds	Supported	Supported
Failover	Not supported	Supported
Standby DB instance migration	Not supported	Supported
Manual primary/standby switchover	Not supported	Supported
Instance class change	Supported	Supported
Storage scale-up	Supported	Supported
Recycle bin	Supported	Supported