Configuring buffer pool size and redo log capacity in MySQL 8.4

In MySQL 8.4, Amazon RDS enables the innodb_dedicated_server parameter by default. With the innodb_dedicated_server parameter, the database engine calculates the innodb_buffer_pool_size and innodb_redo_log_capacity parameters. For information about how these parameters are calculated, see Configuring InnoDB Buffer Pool Size and Redo Log in the MySQL documentation.

With innodb_dedicated_server enabled, the innodb_buffer_pool_size parameter is calculated based on the DB instance class memory. The following table shows the detected server memory and the corresponding buffer pool size.

The innodb_redo_log_capacity parameter automatically scales with the instance class to (number of vCPUs / 2) GB up to a maximum of 16 GB. Larger instance classes have a larger redo log capacity, which can improve performance and resilience for write-intensive workloads.

Before upgrading from MySQL 8.0 to MySQL 8.4, be sure to increase your storage space to accommodate a potential increase in the size of the redo logs that might occur after the upgrade completes. For more information, see Increasing DB instance storage capacity.

If you don't want the innodb_dedicated_server parameter to calculate the values for the innodb_buffer_pool_size and innodb_redo_log_capacity parameters, you can override these values by setting specific values for them in a custom parameter group. Alternatively, you can disable the innodb_dedicated_server parameter and set values for the innodb_buffer_pool_size and innodb_redo_log_capacity parameters in a custom parameter group. For more information, see Default and custom parameter groups.

If you disable the innodb_dedicated_server parameter by setting it to 0 and don't set values for the innodb_buffer_pool_size and innodb_redo_log_capacity parameters, then Amazon RDS sets the latter two parameters to 128 MB and 100 MB, respectively. These defaults result in poor performance on larger instance classes.