I've got a bit of a problem here...

I've got a render-farm full of machines that are writing to a central disk, and, sometimes, after it's written an image sequence (DPX files, 12Mb per frame), about a minute after each file is written, it suddenly drops from 12Mb to 4kb.

I'm pretty certain that there is nothing running that would be doing this. .

The application that is creating the files is Shake.

This problem has cropped up before, very occasionally. I've certainly never figured out what actually causes it.

The central disk is a 10Tb raid, which the machines connect to via NFS.

df -h gives me the following for it:

clarke:/Volumes/projects 8.9Ti 7.7Ti 1.1Ti 88% /mount/projects

So it's not like it's running out of space (I was at 700Gb free when it started having the problem tonight, and I've freed up a load more just in case that was something to do with it...

Any help would be much appreciated! I really want to figure out what's causing this, as it's certainly causing me a lot of pain...


If you want more specs of the server:

  • XServe running OSX Server 10.5.8
  • Promise Raid VTrak E610f

Also: The data certainly was there, for a couple of minutes. I set off a process to copy it to another machine, and that other machine is seeing the images just fine.

More edit:

Is there some kind of tool that will track every single file creation or modification in a folder (or whole file system) and tell me exactly what's going on? I want to find out if there is some kind of rogue process doing something naughty (it works most of the time, so I suspect not) or something lower down than that...

  • Have you examined the contents of the 4kb files to see what they contain? Is it in any way related to what you think should be in the files?
    – ChrisF
    Jan 28 '10 at 22:05
  • Yes - it looks like they are the first 4k of the file that was written.
    – Hugh
    Jan 28 '10 at 22:07
  • 1
    The tool for tracking fs modifications is fs_usage (developer.apple.com/Mac/library/documentation/Darwin/Reference/…). You might also be able to use dtrace (developer.apple.com/mac/library/documentation/Darwin/Reference/…). I think 10.5 supported it, but I am not sure to what degree. Jan 29 '10 at 11:02
  • Thanks Chris - that's fantastic - I'll try that out and see if I can figure it out. My only problem is that it doesn't happen all the time... I'll get that stuff set up though so that I'm ready next time it starts happening.
    – Hugh
    Jan 29 '10 at 11:46
  • Oh, and Chris - feel free to submit that as an answer, and I'll certainly vote it up - it may not solve my problems, but it's definitely useful in figuring them out.
    – Hugh
    Jan 29 '10 at 17:14

Specific to your question about a utility to watch file activity. What you want is called 'opensnoop' and it ships with OS X:


# opensnoop  # (in another terminal 'touch hi')
  UID    PID COMM          FD PATH                 
  502    146 Finder        30 /Users/thedude       
  502   1247 touch          3 /dev/dtracehelper    
  502   1247 touch          3 hi                   
  502    141 Dock          -1 /Users/thedude/Applications
  502    141 Dock           9 /Users/thedude       
  502    141 Dock          11 /Users/thedude       
  502   1225 zsh            3 /var/run/utmpx       
    0     58 mds            9 .                    
  502    850 mdworker       7 /Users/thedude/hi    
  502    146 Finder        30 /Users/thedude      

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