This topic describes the three instance families of ApsaraDB for RDS. They are shared, general-purpose, and dedicated instance families.
|Shared instance family
|General-purpose instance family||
||Users are less concerned with performance and stability.|
|Dedicated instance family||A dedicated instance exclusively occupies the CPU and memory resources allocated to
it. Its performance remains stable for a long term and is not affected by the other
instances that are deployed on the same server.
The top configuration of this instance family is dedicated host. A dedicated host instance occupies all of the resources on the server where it resides.
|Users are engaged in database-centered businesses, such as finance, e-commerce, governmental affairs, and large- and medium-sized Internet services.|
The following figure shows the differences between the three instance families.
The three instance families each have some unique performance metrics and therefore cannot be directly compared. The following table is a comparison of cost-effectiveness between the three instance families by using instance types with similar specifications as examples. This comparison provides a basis for you to make purchase decisions.
|Family||CPU cores and memory capacity||Storage capacity||Maximum number of connections||Maximum IOPS||Monthly subscription fee|
|Shared or general-purpose instance family||4 CPU cores, 16 GB||500 GB||4,000||7,000||USD 320|
|Dedicated instance family||4 CPU cores, 32 GB||500 GB||5,000||9,000||USD 550|
Based on the preceding comparison, a dedicated instance costs 70% more but provides twice as much memory capacity, 25% more connections, and 28% higher input/output operations per second (IOPS) than a shared or general-purpose instance. The dedicated instance family delivers high cost-effectiveness if it is used in suitable business scenarios.
Instance typesFor more information about instance types and their specifications, such as the number of CPU cores, memory capacity, storage capacity, maximum number of connections, and IOPS, see Primary instance types.
For more information about the price of each instance type, visit ApsaraDB RDS for MySQL.
Change the instance family
You can change the family and specifications of your RDS instance based on your business requirements.
For more information, see the following topics:
- Change the specifications of an ApsaraDB RDS for MySQL instance
- Change the specifications of an ApsaraDB RDS for SQL Server instance
- Change the specifications of an ApsaraDB RDS for PostgreSQL instance
- Change the specifications of an ApsaraDB RDS for PPAS instance
- Change the specifications of an ApsaraDB RDS for MariaDB instance
Why does an entry-level instance outperform an enterprise-level instance? An entry-level instance belongs to the shared or general-purpose instance family, whereas an enterprise-level instance belongs to the dedicated instance family.
Therefore, an entry-level instance supports a larger maximum number of connections and delivers higher IOPS than an enterprise-level instance when the same CPU and memory specifications are used. However, an enterprise-level instance is more stable because it exclusively occupies the CPU and memory resources allocated to it. For more information, see Overview.