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  1. Lustre
  2. LU-6414

du and df disagree for used space

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    • Question/Request
    • Resolution: Done
    • Minor
    • None
    • Lustre 2.7.0, Lustre 2.5.3
    • None
    • 9223372036854775807

    Description

      On one of our file systems we have a large discrepancy between the output of du for the whole file system and df (lfs df and standard df report the same numbers), du is reporting about 120TB less disk usage than df (on a ~430TB file system, with 30 OSTs).

      du -xk 224093469629
      df 356924055560

      As the file system is currently ~80% full, this difference is of quite some concern to us.

      My initial suspicion is that there might be some objects allocated on the OSTs which are not reference by files, so don't show up in du, but with Lustre 2.5, I'm not entirely sure anymore how do check this. If I remember correctly at least on 1.8 I would have to run (the e2fsck based) lfsck, ideally with the file system offline/idle, which from memory was fairly invasive. I've tried to read up on the new lfsck but it's not immediately obvious to me a) if this is the right tool and b) how to invoke it to achieve my goal of freeing the ~120TB additional space.

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              yong.fan nasf (Inactive)
              ferner Frederik Ferner (Inactive)
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