MySQL :: MySQL 8.3 Reference Manual :: 17.8.12 Enabling Automatic Configuration for a Dedicated MySQL Server

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17.8.12 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_redo_log_capacity

Note

innodb_log_file_size and innodb_log_files_in_group are deprecated, and are superseded by innodb_redo_log_capacity.
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 innodb_dedicated_server if you run MySQL Server in a Docker container or dedicated VM that only runs MySQL. 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 17.8 Automatically Configured Buffer Pool Size

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

innodb_redo_log_capacity

Redo log capacity is configured according to the amount of memory detected on the server and, in some cases, whether innodb_buffer_pool_size is configured explicitly. If innodb_buffer_pool_size is not configured explicitly, the default value is assumed.

Warning

Automatic redo log capacity configuration behavior is undefined if innodb_buffer_pool_size is set to a value larger than the detected amount of server memory.

Table 17.9 Automatically Configured Log File Size

Detected Server Memory	Buffer Pool Size	Redo Log Capacity
Less than 1GB	Not configured	100MB
Less than 1GB	Less than 1GB	100MB
1GB to 2GB	Not applicable	100MB
2GB to 4GB	Not configured	1GB
2GB to 4GB	Any configured value	round(0.5 * `detected server memory` in GB) * 0.5 GB
4GB to 10.66GB	Not applicable	round(0.75 * `detected server memory` in GB) * 0.5 GB
10.66GB to 170.66GB	Not applicable	round(0.5625 * `detected server memory` in GB) * 1 GB
Greater than 170.66GB	Not applicable	128GB

innodb_log_file_size (deprecated)

Log file size is configured according to the automatically configured buffer pool size.

Table 17.10 Automatically Configured Log File Size

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

innodb_log_files_in_group (deprecated)

The number of log files is configured according to the automatically configured buffer pool size.

Table 17.11 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

Note

The minimum innodb_log_files_in_group value of 2 is enforced if the rounded buffer pool size value is less than 2GB.

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

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.

Data loss is possible if redo log files and data files reside on different storage devices, and an unexpected exit occurs before data file writes are flushed from a device cache that is not battery-backed. If you use or intend to use different storage devices for redo log files and data files, and your data files reside on a device with a cache that is not battery-backed, 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.

If innodb_dedicated_server is enabled and innodb_buffer_pool_size is configured explicitly, variables configured based on buffer pool size use the buffer pool size value calculated according to the amount of memory detected on the server rather than the explicitly defined buffer pool size value.

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

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