What does "ext4: Unaligned AIO/DIO on inode X by processY: performance will be poor" messages mean on Red Hat Enterprise Linux?
Issue
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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/messageson 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 poorWhat does it mean? What can we do prevent it?
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In my
/var/log/messagesfile, 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
- Applications observed to cause this problem so far include: miscellaneous java applications, HornetQ, SAP, MRG Messaging (
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