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Stu Thompson
Asked: 2009-05-01 02:00:59 +0800 CST

ext3 file system performance tuning: what metrics to monitor

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I have a high-IO application that is working, and scaling well to date. Over the past few months we've been trying to look down the road and predict where our next bottlenecks will occur. One of them is surely the file system.

We are currently monitoring

  • Space available
  • Read operations per second
  • Write operations per second

This seems a bit too sparse to me. What else should I be watching? I am not even sure what the 'yellow line' would be for the operations/second.

performance monitoring ext3 tuning

1 Answers

  1. Best Answer

    Some suggestions

    • Look at the read queue size, if your application is highly random, then tweak the readahead in /sys/block/<dev>/queue/read_ahead_kb to ensure you're reading data you need, not data the OS thinks you need.
    • Switch to the deadline scheduler if you haven't already
    • use the noatime mount option unless you're hosting a mail spool
    • mount with data=writeback if you've got good backups
    • keep an eye on your directory sizes, sure hashed directory inodes help, but if you can hash the data yourself then you'll get more consistent results
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