From RHEL-RT

Filesystem Determinism - HOWTO

• Journal activity can introduce latency
  • Ordering changes, committing metadata, committing data
  • Third-party filesystems can do the wrong thing
  • Especially if they re-implement their own untuneable bdflush

• Don't journal when you don't have to
  • A journal is designed to speed recovery from a crash
  • Is your data valuable 20 minutes after a crash?
  • Consider using ext2 instead of ext3
    • NOTE: In many of our best benchmark results, we utilize the ext2 filesystem rather than ext3. Hence, this tip should be considered among the top initial tuning recommendations.

• Don't write when you don't have to (noatime, ro)
  • For a description of how to diasble the atime mount option, refer here: RHEL-RT SystemTuningNoAtime

• Try different I/O elevators
  • $ echo deadline > /sys/block/<sdx>/queue/scheduler