This topic describes how to configure the innodb_buffer_pool_size parameter of an ApsaraDB RDS for MySQL instance based on your business requirements to improve the performance of the RDS instance.
Prerequisites
The RDS instance runs one of the following RDS editions:
RDS High-availability Edition
RDS Basic Edition
RDS Cluster Edition
Limits
You cannot modify the value of the innodb_buffer_pool_size parameter for a serverless RDS instance. The size of the InnoDB buffer pool varies based on the specifications of the serverless RDS instance.
Background information
You can reconfigure the innodb_buffer_pool_size parameter to change the size of the InnoDB buffer pool for an RDS instance. The value of this parameter is calculated by using the following formula:
{DBInstanceClassMemory*X/Y} Example:
{DBInstanceClassMemory*7/10}DBInstanceClassMemory is a system variable, which specifies the memory capacity of the RDS instance.
X is the numerator, and Y is the denominator.
The size of the InnoDB buffer pool must be within the following range: [128 MB, DBInstanceClassMemory × 8/10]. The minimum size is 128 MB. The maximum size is 80% of the memory capacity that you purchased for the RDS instance.
The default size of the InnoDB buffer pool for an RDS instance is calculated based on the following rules:
If the RDS instance is a general-purpose instance that uses cloud disks or the RDS instance uses local disks, the default size of the InnoDB buffer pool is calculated by using the following formula:
Default size of the InnoDB buffer pool = Purchased memory capacity of the RDS instance × 0.75.If the RDS instance is a dedicated instance that uses cloud disks, the default size of the InnoDB buffer pool is calculated by using the following formula:
Default size of the InnoDB buffer pool = (Purchased memory capacity of the RDS instance - Reserved memory capacity of the RDS instance) × 0.75.NoteIf the RDS instance is a dedicated instance that uses cloud disks, the reserved memory capacity in MB of the RDS instance is calculated by using the following formula:
MIN(Purchased memory capacity of the RDS instance/2, 2048) + MAX(Number of CPU cores of the RDS instance × 64, Purchased memory capacity of the RDS instance/64) + (Purchased memory capacity of the RDS instance/64) + 285The default size of the InnoDB buffer pool is an integer multiple of 128. If the calculated result is not an integer multiple of 128, the result is rounded to the nearest integer that is a multiple of 128. For example, an RDS instance provides 1,024 MB of memory, the calculated result is 268, and the nearest integer that is a multiple of 128 is 256. In this case, the default size of the InnoDB buffer pool for the RDS instance is 256 MB.
The following table provides the default size and maximum size of the InnoDB buffer pool for a dedicated RDS instance that uses cloud disks.
Number of CPU cores | Memory capacity (unit: MB) | Default buffer pool size (unit: MB) | Maximum buffer pool size (Unit: MB) |
2 | 4,096 | 1,024 | 1,024 |
2 | 8,192 | 4,096 | 4,096 |
2 | 16,384 | 9,216 | 10,240 |
4 | 8,192 | 4,096 | 4,096 |
4 | 16,384 | 9,216 | 10,240 |
4 | 32,768 | 21,504 | 22,528 |
8 | 16,384 | 9,216 | 10,240 |
8 | 32,768 | 21,504 | 22,528 |
8 | 65,536 | 45,056 | 48,128 |
12 | 24,576 | 15,360 | 16,384 |
12 | 49,152 | 33,792 | 35,840 |
12 | 98,304 | 69,632 | 73,728 |
16 | 32,768 | 21,504 | 22,528 |
16 | 65,536 | 45,056 | 48,128 |
16 | 131,072 | 93,184 | 99,328 |
24 | 49,152 | 32,768 | 34,816 |
24 | 98,304 | 69,632 | 73,728 |
24 | 196,608 | 140,288 | 149,504 |
32 | 65,536 | 45,056 | 47,104 |
32 | 131,072 | 93,184 | 99,328 |
32 | 262,144 | 188,416 | 200,704 |
52 | 98,304 | 67,584 | 72,704 |
52 | 196,608 | 140,288 | 149,504 |
52 | 393,216 | 283,648 | 302,080 |
64 | 262,144 | 188,416 | 200,704 |
64 | 524,288 | 378,880 | 403,456 |
102 | 786,432 | 569,344 | 607,232 |
104 | 196,608 | 138,240 | 147,456 |
104 | 393,216 | 282,624 | 302,080 |
The size of the InnoDB buffer pool must be an integer multiple of the result that is obtained by using the following formula: Value of the innodb_buffer_pool_chunk_size parameter × Value of the innodb_buffer_pool_instances parameter. If the size of the InnoDB buffer pool is not an integer multiple of the result that you obtain by using the formula, ApsaraDB RDS changes the size to an integer multiple of the result. For example, if the result that you obtain by using the formula is 1 GB and you set the innodb_buffer_pool_size parameter to 1.5 GB, ApsaraDB changes the value of the innodb_buffer_pool_size parameter to 2 GB.
Change the size of the InnoDB buffer pool for a single RDS instance
- Go to the Instances page. In the top navigation bar, select the region in which the RDS instance resides. Then, find the RDS instance and click the ID of the instance.
In the left-side navigation pane, click Parameters.
Find the innodb_buffer_pool_size parameter and click the
icon. In the dialog box that appears, enter a new value and click OK. 
Click Apply Changes. In the dialog box that appears, click OK.
NoteAfter you modify the innodb_buffer_pool_size parameter of an RDS instance that runs MySQL 5.6, you must wait for the RDS instance to restart. After you modify the innodb_buffer_pool_size parameter of an RDS instance that runs MySQL 5.7 or MySQL 8.0, you do not need to wait for the RDS instance to restart.
Change the size of the InnoDB buffer pool for multiple RDS instances at a time
You can create a parameter template that contains the innodb_buffer_pool_size parameter. Then, you can apply the template to multiple RDS instances to change the size of the InnoDB buffer pool for these RDS instances at a time. If a parameter template that contains this parameter has been created, you need to only change the value of this parameter in the template. Then, you can apply the template to multiple RDS instances at a time. For more information, see Use a parameter template.
