Instance families


Instance family	Description	Use scenario
Shared instance family	Shared RDS instances enjoy dedicated memory and storage resources, but share CPU resources with the other shared instances that are deployed on the same physical host. CPU resources are highly reused among the shared RDS instances that are deployed on the same physical host. The reuse of CPU resources helps maximize cost-effectiveness. Shared RDS instances that are deployed on the same physical host may compete for resources.	You want an inexpensive database option. You require high availability rather than high stability from your ApsaraDB RDS for SQL Server instance. The shared instance family is supported only for RDS instances that run SQL Server.
General-purpose instance family	General-purpose RDS instances that use local SSDs enjoy dedicated memory resources, but share CPU and storage resources with the other general-purpose instances that are deployed on the same physical host. Storage resources of general-purpose RDS instances that use standard SSDs or enhanced SSDs (ESSDs) are decoupled from compute resources (CPU cores and memory). You can independently scale storage resources. Among the CPU cores provided by a general-purpose RDS instance, some are dedicated to that instance, while the other cores are shared with the other general-purpose RDS instances that are deployed on the same physical host. In this case, contention for CPU resources occur less when compared with shared RDS instances.	You do not require high stability for your databases.
Dedicated instance family	Dedicated instances enjoy dedicated CPU and memory resources. The performance of a dedicated RDS instance is guaranteed and is not affected by the other instances that are deployed on the same physical host. In the dedicated instance family, dedicated host instance types have the highest specifications. A dedicated host RDS instance occupies all the resources of the physical host on which the RDS instance is deployed.	Your databases are used as core systems in sectors such as finance, e-commerce, public services, and large-sized or medium-sized Internet services.

Instance types

For more information about the supported instance types and their specifications, such as the number of cores, memory capacity, storage capacity, maximum number of connections, and input/output operations per second (IOPS), see Primary ApsaraDB RDS instance types.

Pricing

For more information about the prices of different instance types, visit the ApsaraDB RDS buy page.

Instance family change

You can change the instance type of your RDS instance to an instance type that belongs to a different instance family based on your business requirements.

Note You cannot change the instance type of your RDS instance from a shared instance type to an instance type that belongs to a different instance family. If you want to switch from the shared instance family to a different instance family, you can create an RDS instance that uses the new instance type and then use Data Transmission Service (DTS) to migrate the data of your RDS instance to the new RDS instance. For more information, see Data migration solutions.

For more information about how to change the instance type of your RDS instance, see the following topics:

FAQ

It seems that general-purpose instances outperform dedicated instances that have the same CPU and memory specifications. Why should I choose the dedicated instance family?

A dedicated RDS instance enjoys dedicated CPU and memory resources, whereas a general-purpose RDS instance enjoys only dedicated memory resources. Therefore, the dedicated instance offers more reliable performance in actual practice. For more information, see Instance families.