[ET Trac] [Einstein Toolkit] #1772: Simfactory: potentially serious problem with CACHE directory in the simulations directory
Einstein Toolkit
trac-noreply at einsteintoolkit.org
Tue May 5 21:36:21 CDT 2015
#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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