What does "ext4: Unaligned AIO/DIO on inode X by processY: performance will be poor" messages mean on Red Hat Enterprise Linux?

Solution Verified - Updated -

Issue

  • The following message was seen in the logs:

    ext4: Unaligned AIO/DIO on inode 12 by dataserver: performance will be poor.

  • We are migrating our SAP infrastructure to RHEL 6.1. After installation several errors occur in the /var/log/messages on all our two test servers regularly.

    # grep align /var/log/messages
kernel: EXT4-fs (dm-23): Unaligned AIO/DIO on inode 131078 by oracle; performance will be poor.
kernel: EXT4-fs (dm-20): Unaligned AIO/DIO on inode 131078 by oracle; performance will be poor.

  • We found the following error message in dmesg in one of our servers:

    EXT4-fs (dm-0): Unaligned AIO/DIO on inode 673075 by java; performance will be poor

    What does it mean? What can we do prevent it?

  • In my /var/log/messages file, I see the following:

    kernel: EXT4-fs (dm-6): Unaligned AIO/DIO on inode 131370 by java; performance will be poor.

    The inode referenced is file: /mdev/local/jboss/jbc7/node2/data/hornetq/journal/hornetq-data-1.hq
    I would prefer that performance NOT be poor... How can I resolve this?

Environment

  • Red Hat Enterprise Linux 5.6 and later
  • Red Hat Enterprise Linux 6.0 and later
  • Ext4 filesystem
    • Application must be writing to a file with asynchronous direct I/O (AIO)
    • Must be using unaligned writes (meaning it must be writing to a portion of a filesystem block).
    • Writes require allocation of disk blocks and/or conversion of unwritten extents.
  • Any application that does not ensure block-aligned AIO writes can cause this issue.
    • Applications observed to cause this problem so far include: miscellaneous java applications, HornetQ, SAP, MRG Messaging (qpid), qemu-kvm

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