Instance types for read-only ApsaraDB RDS instances - ApsaraDB RDS

ApsaraDB RDS allows you to create read-only RDS instances 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 instance types for primary RDS instances, see Primary ApsaraDB RDS instance types.

Read-only instance types for different database engines

Instance types for standard read-only ApsaraDB RDS for MySQL instances (original x86 architecture)
Instance types for YiTian read-only ApsaraDB RDS for MySQL instances (original ARM architecture)
Instance types for read-only ApsaraDB RDS for PostgreSQL instances
Instance types for read-only ApsaraDB RDS for SQL Server instances

IOPS

The maximum IOPS of an RDS instance that uses local disks is determined solely by its instance type, and the maximum IOPS of an RDS instance that uses cloud disks is determined by its instance type and storage capacity. The following table describes the formulas that are used to calculate the maximum IOPS of an RDS instance equipped with cloud disks.

Note If the throughput of an RDS instance reaches the upper limit, the maximum IOPS of the RDS instance may not be delivered.

Storage type ESSD Standard SSD

PL PL3 PL2 PL1 N/A

Formula

(Unit: 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}

Take min{1800 + 50 × Storage capacity, 50000, Maximum IOPS for the instance type} as an example of how to calculate the maximum IOPS for an instance equipped with an enhanced SSD (ESSD) of performance level 1 (PL1). The following section explains the values and their roles in the formula:

min: a function that compares the values within the brackets and returns the smallest value.
1800 + 50 × Storage capacity: the baseline IOPS that is supported by the equipped ESSD.
50000: the maximum IOPS that is supported by the equipped ESSD. In this example, a PL1 ESSD is used. The maximum IOPS varies based on the storage type and its PL. 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 Instance types for primary RDS instances that run different database engines.
For more information about the performance of cloud disks, see EBS performance.

The maximum IOPS equals the smallest of the three values stated in the preceding list. In the following examples, two RDS instances equipped with PL1 ESSDs are used. They are both of the mysql.x2.large.2c instance type that provides a maximum IOPS of 20,000.

The first RDS instance has a storage capacity of 20 GB. According to the formula provided in the preceding section, the baseline IOPS is calculated as 1800 + 50 × 20 = 2800. The three IOPS values are 2,800, 50,000, and 20,000, among which 2,800 is the smallest value. Therefore, the maximum IOPS of the RDS instance is 2,800.
The second RDS instance has a storage capacity of 6,000 GB. According to the formula provided in the preceding section, the baseline IOPS is calculated as 1800 + 50 × 6000 = 301800. The three IOPS values are 301,800, 50,000, and 20,000, among which 20,000 is the smallest value. 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 four I/O.
In the specification tables that are provided in this topic, if the maximum IOPS and maximum I/O bandwidth (measured in 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.

Pricing

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

For more information about the prices of pay-as-you-go read-only RDS instances, see the following files:
For more information about the prices of subscription read-only RDS instances, see the following files:

For more information about the prices of the storage capacity that you select for read-only RDS instances, visit the ApsaraDB RDS buy page.