Apache Ignite Direct IO Module

Apache Ignite Direct IO is plugin, which provides page store with ability to write and read cache partitions in O_DIRECT mode.

OS gets the data and stores it in a file buffer cache (Page Cache).

Similarly, for every write operation, the OS first writes the data in a cache and then transfers to the disk. To eliminate this process you can enable Direct I/O in which case the data is read and written directly from/to the disk bypassing the file buffer cache.

Direct I/O plugin in Ignite is used for the checkpointing process where the dirty pages in RAM are written to the disk.

Importing Direct I/O Pluging In Maven Project

If you are using Maven to manage dependencies of your project, you can add Direct IO Module dependency like this (replace ‘${ignite.version}’ with actual Ignite version you are interested in):

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
                        http://maven.apache.org/xsd/maven-4.0.0.xsd">
    ...
    <dependencies>
        ...
        <dependency>
            <groupId>org.apache.ignite</groupId>
            <artifactId>ignite-direct-io</artifactId>
            <version>${ignite.version}</version>
        </dependency>
        ...
    </dependencies>
    ...
</project>

Importing Direct I/O Pluging In Gradle Project

For gradle you can add compile dependency, where igniteVersion is actual Ignite version:

compile group: 'org.apache.ignite', name: 'ignite-direct-io', version: igniteVersion

Additional setup is not required. Once plugin is available in classpath, it will be used for Durable Memory IO.

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See more information in Apache Ignite documentation: How to enable Direct IO

and description of internal desing can be found in Wiki: Under the hood: Direct IO