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Chapter 10. Minimizing or avoiding system slowdowns due to journaling

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The order in which journal changes are written to disk might differ from the order in which they arrive. The kernel I/O system can reorder the journal changes to optimize the use of available storage space. Journal activity can result in system latency by re-ordering journal changes and committing data and metadata. As a result, journaling file systems can slow down the system.

XFS is the default file system used by RHEL 8. This is a journaling file system. An older file system called ext2 does not use journaling. Unless your organization specifically requires journaling, consider the ext2 file system. In many of Red Hat’s best benchmark results, the ext2 filesystem is used. This is one of the top initial tuning recommendations.

Journaling file systems like XFS, records the time a file was last accessed (the atime attribute). If you need to use a journaling file system, consider disabling atime.

10.1. Disabling atime

Disabling the atime attribute increases performance and decreases power usage by limiting the number of writes to the file-system journal.

Procedure

  1. Open the /etc/fstab file using your chosen text editor and locate the entry for the root mount point.

    /dev/mapper/rhel-root       /       xfs    defaults…
  2. Edit the options sections to include the terms noatime and nodiratime. The noatime option prevents access timestamps being updated when a file is read, and the nodiratime option stops directory inode access times being updated.

    /dev/mapper/rhel-root       /       xfs    noatime,nodiratime…
Important

Some applications rely on atime being updated. Therefore, this option is reasonable only on systems where such applications are not used.

Alternatively, you can use the relatime mount option, which ensures that the access time is only updated if the previous access time is older than the current modify time.

10.2. Additional resources

  • mkfs.ext2(8) man page
  • mkfs.xfs(8) man page
  • mount(8) man page
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