MySQL :: MySQL 8.0 Reference Manual :: 15.8.12 Enabling Automatic Configuration for a Dedicated MySQL Server

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15.8.12 Enabling Automatic Configuration for a Dedicated MySQL Server

When innodb_dedicated_server is enabled, InnoDB automatically configures the following variables:

innodb_buffer_pool_size
innodb_log_file_size
innodb_log_files_in_group (as of MySQL 8.0.14)
innodb_flush_method

Only consider enabling innodb_dedicated_server if the MySQL instance resides on a dedicated server where it can use all available system resources. For example, consider enabling if you run MySQL Server in a Docker container or dedicated VM. Enabling innodb_dedicated_server is not recommended if the MySQL instance shares system resources with other applications.

The information that follows describes how each variable is automatically configured.

innodb_buffer_pool_size

Buffer pool size is configured according to the amount of memory detected on the server.

Table 15.9 Automatically Configured Buffer Pool Size

Detected Server Memory	Buffer Pool Size
Less than 1GB	128MiB (the default value)
1GB to 4GB	`detected server memory` * 0.5
Greater than 4GB	`detected server memory` * 0.75

innodb_log_file_size

As of MySQL 8.0.14, log file size is configured according to the automatically configured buffer pool size.

Table 15.10 Automatically Configured Log File Size

Buffer Pool Size	Log File Size
Less than 8GB	512MiB
8GB to 128GB	1024MiB
Greater than 128GB	2048MiB

Note

Prior to MySQL 8.0.14, the innodb_log_file_size variable was automatically configured according to the amount of memory detected on the server, as shown below:

Table 15.11 Automatically Configured Log File Size (MySQL 8.0.13 and Earlier)

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

innodb_log_files_in_group

The number of log files is configured according to the automatically configured buffer pool size (in gigabytes). Automatic configuration of the innodb_log_files_in_group variable was added in MySQL 8.0.14.

Table 15.12 Automatically Configured Number of Log Files

Buffer Pool Size	Number of Log Files
Less than 8GB	ROUND(`buffer pool size`)
8GB to 128GB	ROUND(`buffer pool size` * 0.75)
Greater than 128GB	64

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.
InnoDB uses O_DIRECT during flushing I/O, but skips the fsync() system call after each write operation.

Warning

Prior to MySQL 8.0.14, this setting is not suitable for file systems such as XFS and EXT4, which require an fsync() system call to synchronize file system metadata changes.
As of MySQL 8.0.14, fsync() is called after creating a new file, after increasing file size, and after closing a file, to ensure that file system metadata changes are synchronized. The fsync() system call is still skipped after each write operation.
On storage devices with cache, data loss is possible if data files and redo log files reside on different storage devices, and a crash occurs before data file writes are flushed from the device cache. If you use or intend to use different storage devices for redo logs and data files, use O_DIRECT instead.

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_log_files_in_group are automatically configured based on the implicit buffer pool size that is calculated according to the amount of memory detected on the server.

Automatically configured settings are evaluated and reconfigured if necessary each time the MySQL server is started.

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