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Updated on 2025-12-26 GMT+08:00
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RDS for SQL Server Product Series

RDS for SQL Server DB instances are classified into the following types:
  • Single
  • Primary/Standby
  • Cluster
Table 1 DB instance types

DB Instance Type

Description

Notes

Scenarios

Single

A single-node architecture is more cost-effective than a primary/standby DB pair.

If a fault occurs on a single instance, the instance cannot recover in a timely manner.
  • Personal learning
  • Microsites
  • Development and testing environment of small- and medium-sized enterprises

Primary/Standby

An HA architecture. A pair of primary and standby DB instances shares the same IP address and can be deployed in different AZs.
  • 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.
  • Production databases of large and medium enterprises
  • Applications for the Internet, Internet of Things (IoT), retail e-commerce sales, logistics, gaming, and other industries

Cluster

The Microsoft Always On architecture. There is one primary node, one standby node, and up to five read-only nodes. It features higher availability, reliability, and scalability.

Only for RDS for SQL Server.
  • Finance industry
  • Internet industry
  • Hotel industry
  • Online education

Advantage Comparison

  • Single-node DB instances support read replicas and allow you to query error logs and slow query logs. Different from primary/standby DB instances that have two database nodes, a single-node DB instance has only one node, reducing the price. If the node fails, the restoration will take a long time. Therefore, single DB instances are not recommended for sensitive services that have high requirements on database availability.
  • Primary/Standby DB instances use the standby database node only for failover and restoration. The standby database node does not provide services. The performance of single DB instances is similar to or even higher than primary/standby DB instances because standby nodes cause extra performance overhead.
Table 2 Function comparisons

Function

Single

Primary/Standby

Number of nodes

1

2

Specifications

vCPUs: a maximum of 60

Memory: a maximum of 512 GB

Storage: a maximum of 4,000 GB

vCPUs: a maximum of 60

Memory: a maximum of 512 GB

Storage: a maximum of 4,000 GB

Monitoring and alarms

Supported

Supported

Security group

Supported

Supported

Backup and restoration

Supported

Supported

Recycle bin

Supported

Supported

Parameter settings

Supported

Supported

SSL

Supported

Supported

Log management

Supported

Supported

Read replicas (which need to be created)

Not supported

Not supported

High-frequency monitoring

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
Parent topic: Product Series