This topic provides an overview of read-only ApsaraDB RDS instance types. This overview includes the most recent instance types and the specifications for each instance type.

ApsaraDB RDS allows you to create read-only RDS instances. These read-only RDS instances are used to increase the read capability of your database system. For more information about read-only RDS instances, see Overview of read-only ApsaraDB RDS for MySQL instances.

For more information about primary ApsaraDB RDS instance types, see Primary ApsaraDB RDS instance types.

Read-only instance types for different database engines

Maximum IOPS for standard SSDs and ESSDs

The maximum IOPS of an RDS instance that is equipped with local SSDs varies based on the instance type. The maximum IOPS of an RDS instance that is equipped with standard SSDs or enhanced SSDs (ESSDs) varies based on the instance type and the storage capacity. The following table lists the formulas that are used to calculate the maximum IOPS of an RDS instance equipped with standard SSDs or ESSDs.

Note If the throughput of an RDS instance reaches the upper limit, the IOPS that the RDS instance can deliver is affected.
Storage type ESSD Standard SSD
PL PL3 PL2 PL1 None

Formula

(The storage capacity is measured in the unit of GB.)

min{1800 + 50 × Storage capacity, 1000000, Maximum IOPS for the instance type} min{1800 + 50 × Storage capacity, 100000, Maximum IOPS for the instance type} min{1800 + 50 × Storage capacity, 50000, Maximum IOPS for the instance type} min{1800 + 30 × Storage capacity, 25000, Maximum IOPS for the instance type}
The min{1800 + 50 × Storage capacity, 50000, Maximum IOPS for the instance type} formula is used as an example to describe the IOPS values in the preceding table.
  • min: specifies that the smallest IOPS among the three IOPS values in the formula is considered the maximum IOPS of the RDS instance.
  • 1800 + 50 × Storage capacity: the baseline IOPS that is supported by each ESSD of PL1.
  • 50000: the maximum IOPS that is supported by each ESSD of PL1. The maximum IOPS varies based on the storage type. For more information, see ESSDs.
  • Maximum IOPS for the instance type: the maximum IOPS that is supported by the instance type of the Elastic Compute Service (ECS) instance on which the RDS instance is deployed. For more information about the maximum IOPS for each instance type, see the specification tables that are provided in this topic.
The smallest IOPS among the three IOPS values in the applicable formula is considered the maximum IOPS of the RDS instance.
  • In the following examples, an RDS instance that is equipped with ESSDs of PL1 is used. The instance type is mysql.x2.large.2c, the maximum IOPS for the instance type is 20,000, and the storage capacity is 20 GB. In this example, the baseline IOPS is 2,800 based on the following calculation: 1800 + 50 × 20 = 2800. The smallest IOPS among the three IOPS values in the applicable formula is 2,800. Therefore, the maximum IOPS of the RDS instance is 2,800.
  • In the following examples, an RDS instance that is equipped with ESSDs of PL1 is used. The instance type is mysql.x2.large.2c, and the maximum IOPS for the instance type is 20,000. In this example, if the storage capacity of the RDS instance exceeds 6,000 GB, the baseline IOPS is 301,800. The smallest IOPS among the three IOPS values in the applicable formula is 20,000. Therefore, the maximum IOPS of the RDS instance is 20,000.
Note
  • If the maximum I/O bandwidth of the RDS instance is reached, the RDS instance may fail to deliver the maximum IOPS.
  • The baseline IOPS of an ECS cloud disk allows you to read and write 4 KB of data per second. The default IOPS that is supported by MySQL allows you to read and write 16 KB of data. Therefore, each read/write operation on MySQL consumes 4 IOPS.
  • In the specification tables that are provided in this topic, if the maximum IOPS and maximum I/O bandwidth Mbit/s for an instance type are marked as None, ApsaraDB RDS allows multiple instances of the instance type to preempt resources. In this case, the IOPS is not limited. The maximum I/O bandwidth is measured in the unit of Mbit/s.

Pricing

For more information about the prices of read-only RDS instances, see the following file:

Prices of Subscription Read-only ApsaraDB RDS for MySQL Instances (Specifications)

For more information about the prices of pay-as-you-go RDS instances and storage capacities:

The price of the RDS instance that you want to purchase varies based on the instance configuration, such as the region, instance type, storage capacity that you select. For more information, visit the ApsaraDB RDS buy page.