This topic describes the instance families of ApsaraDB RDS. ApsaraDB RDS supports the shared instance family, general-purpose instance family, and dedicated instance family.

Instance families

Instance family Description Scenarios
Shared instance family
  • A shared RDS instance exclusively occupies the allocated memory and storage resources, but shares CPU resources with the other shared RDS 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 pursue high cost-effectiveness to reduce costs.
  • You require high availability rather than high performance stability from your ApsaraDB RDS for SQL Server instance.
General-purpose instance family
  • A general-purpose RDS instance exclusively occupies the allocated memory resources, but shares CPU and storage resources with the other general-purpose RDS instances that are deployed on the same physical host.
  • CPU resources are moderately reused among the general-purpose RDS instances that are deployed on the same physical host. The reuse of CPU resources helps increase cost-effectiveness.
  • The storage capacity of a general-purpose RDS instance is independent of the number of cores and the memory capacity. You can specify the storage capacity based on your business requirements.
You do not require high performance stability.
Dedicated instance family
  • A dedicated RDS instance exclusively occupies the allocated CPU and memory resources. The performance of a dedicated RDS instance remains stable and is not affected by the other instances that are deployed on the same physical host.
  • Dedicated host instance types are the highest instance types in the dedicated instance family. A dedicated host RDS instance occupies all resources on the physical host on which the RDS instance is deployed.
You use databases as core systems in sectors such as finance, e-commerce, public affairs, and large-sized or medium-sized Internet services.
Figure 1. Comparison among instance families
ApsaraDB RDS instance families

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 IOPS, see Primary ApsaraDB RDS instance types.

Pricing

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

Change of the instance family

You can change the instance type of your RDS instance between a dedicated instance type and a general-purpose instance type 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 change the instance type of your RDS instance from a shared instance type to an instance type that belongs 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 to an instance type that belongs to a different instance family, see the following topics:

FAQ

A general-purpose RDS instance and a dedicated RDS instance are allocated the same number of cores and the same amount of memory. Why does the general-purpose RDS instance support a larger maximum number of connections and deliver higher IOPS than the dedicated RDS instance?

A dedicated RDS instance exclusively occupies the allocated CPU and memory resources, whereas a general-purpose RDS instance exclusively occupies only the allocated memory resources. Therefore, a general-purpose RDS instance delivers higher performance than a dedicated RDS instance due to flexible resource scheduling. However, a dedicated RDS instance provides higher performance stability than a general-purpose RDS instance. For more information, see the "Instance families" section of the topic.