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MySQL 8.0 Reference Manual  /  ...  /  Enabling Automatic Configuration for a Dedicated MySQL Server

15.8.12 Enabling Automatic Configuration for a Dedicated MySQL Server

When innodb_dedicated_server is enabled, InnoDB automatically configures the following options according to the amount of memory detected on the server:

  • innodb_buffer_pool_size

    Table 15.7 Automatically Configured Buffer Pool Size

    Detected Server Memory Buffer Pool Size
    < 1G 128MiB (the innodb_buffer_pool_size default)
    <= 4G Detected server memory * 0.5
    > 4G Detected server memory * 0.75

  • innodb_log_file_size

    Table 15.8 Automatically Configured Log File Size

    Detected Server Memory Log File Size
    < 1GB 48MiB (the innodb_log_file_size default)
    <= 4GB 128MiB
    <= 8GB 512MiB
    <= 16GB 1024MiB
    > 16GB 2048MiB

  • innodb_flush_method

    The flush method is set to O_DIRECT_NO_FSYNC when innodb_dedicated_server is enabled. If the O_DIRECT_NO_FSYNC setting is not available, the default innodb_flush_method setting is used.


    Prior to MySQL 8.0.14, the O_DIRECT_NO_FSYNC setting is not recommended for use on Linux systems. It may cause the operating system to hang due to file system metadata becoming unsynchronized. As of MySQL 8.0.14, InnoDB calls fsync() after creating a new file, after increasing file size, and after closing a file, which permits O_DIRECT_NO_FSYNC mode to be safely used on XFS and EXT4 file systems. The fsync() system call is still skipped after each write operation.

Only consider enabling this option if your MySQL instance runs on a dedicated server where the MySQL server is able to consume all available system resources. Enabling this option is not recommended if your MySQL instance shares system resources with other applications.

If an automatically configured option is configured explicitly in an option file or elsewhere, the explicitly specified setting is used and a startup warning similar to this is printed to stderr:

[Warning] [000000] InnoDB: Option innodb_dedicated_server is ignored for innodb_buffer_pool_size because innodb_buffer_pool_size=134217728 is specified explicitly.

Explicit configuration of one option does not prevent the automatic configuration of other options. For example, if innodb_dedicated_server is enabled and innodb_buffer_pool_size is configured explicitly in an option file, innodb_log_file_size and innodb_flush_method are still subject to automatic configuration.

Automatically configured settings are reevaluated according to the amount of detected server memory each time the MySQL server is started. If the amount of detected server memory changes, the automatically configured settings are adjusted accordingly.

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