Function Comparison

Single DB instances use a single-node architecture. Different from the primary/standby DB instances, a single DB instance contains only one node and has no slave node for fault recovery.

Advantage Comparison

  • Single DB instances: support the creation of read replicas and support the queries of error logs and slow query logs. Different from primary/standby DB instances that have two database nodes, a single DB instance has only one node. If a 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 slave database node only for failover and restoration. The slave database node does not provide services. The performance of single DB instances is similar to or even higher than the primary/standby DB instances.

  • Cluster instances: use the Microsoft Always On architecture with one master node, one slave node, and up to five read-only nodes. It features higher availability, reliability, and scalability.

Table 1 Function comparisons

Function

Single

Primary/Standby

Cluster

Number of nodes

1

2

2

Specifications

vCPUs: a maximum of 32

Memory: a maximum of 128 GB

Storage: a maximum of 4,000 GB

vCPUs: a maximum of 32

Memory: a maximum of 128 GB

Storage: a maximum of 4,000 GB

vCPUs: a maximum of 64

Memory: a maximum of 512 GB

Storage: a maximum of 4 TB

Monitoring and alarms

Supported

Supported

Supported

Security group

Supported

Supported

Supported

Backups and restorations

Supported

Supported

Supported

Recycle bin

Supported

Supported

Supported

Parameter settings

Supported

Supported

Supported

SSL

Supported

Supported

Supported

Log management

Supported

Supported

Supported

Read replicas (need to be created)

Supported

Supported

Supported

High-frequency monitoring

Supported

Supported

Supported

Primary/standby switchover or failover

Not supported

Supported

Supported

Standby DB instance migration

Not supported

Supported

Supported

Manual primary/standby switchover

Not supported

Supported

Supported

Instance class change

Supported

Supported

Supported