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fdatasync()

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Last updated: 2025-08-14 17:30:31

Overview

The fsync() system call flushes redo logs to disk, including metadata and data. But metadata contains unimportant information such as the last modified time. You can enable the fdatasync() system call to skip metadata when flushing redo logs in order to reduce costs.

Supported Versions

Kernel version: MySQL 5.7 20201230 and above.
Kernel version: MySQL 8.0 20201230 and above.

Use Cases

This feature is suitable for use cases with heavy write pressure.

Performance Data

TPS is improved by about 10%, according to the sysbench test in a high-concurrency continuous write scenario using the oltp_write_only.lua script.

Instructions

Use the innodb_flush_redo_using_fdatasync parameter to enable or disable fdatasync(). Valid values: true (enable), false (disable). Default value: false. If fdatasync() is enabled, metadata of redo logs won't be flushed to disk in real time.
Parameter
Effective Immediately
Type
Default Value
Valid Values/Value Range
Description
innodb_flush_redo_using_fdatasync
Yes
bool
true
true/false
Whether to call fdatasync() to flush redo logs
Note:
Currently, users cannot modify the values of the above parameters directly. If they need to be modified, submit a ticket for modification.
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