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fdatasync()

Last updated: 2021-12-22 16:25:13

    Feature 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.

    Use 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 false true/false Whether to call fdatasync() to flush redo logs
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