[ET Trac] [Einstein Toolkit] #1772: Simfactory: potentially serious problem with CACHE directory in the simulations directory

[Einstein Toolkit]

#1772: Simfactory: potentially serious problem with CACHE directory in the
simulations directory
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  Reporter:  bmundim     |       Owner:                     
      Type:  defect      |      Status:  new                
  Priority:  critical    |   Milestone:  ET_2015_05         
 Component:  SimFactory  |     Version:  development version
Resolution:              |    Keywords:  CACHE              
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Comment (by eschnett):

 If there is a machine where creating a hard link leads to a soft link
 being created, then someone needs to get a stern talking-to. They have
 very different behaviour, and this leads to exactly the problem you
 describe. I assume that Loewe may have a file system that doesn't support
 hard links, and that someone decided to use file system options that
 replaces hard links by soft links. I'm not happy.

 That's exactly the reason why Simfactory is so complex: It's not that
 things are difficult, it's that each HPC system is its own fiefdom that
 does things every so slightly differently than others. To provide a
 uniform interface, one needs to check all the corner cases.

 What machine and what file system is Loewe?



 Regarding file size vs. number of files: No, it is really the file size
 that makes the difference, not the number of files.

 The fallback when a hard link cannot be created (e.g. on a Blue Gene/Q,
 which does not support hard links) is to copy files instead. In this case
 the cache becomes meaningless.

 In my steps above, the cache is not updated at step 1. It is only updated
 (or created if need be) in step 6, after the simulation has the correct
 executable.

 And with "right executable" I mean that it is the same executable, byte
 for byte, as determined by an actual comparison, as the one in the source
 tree.

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/1772#comment:5>
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