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On Feb 3, 2022, at 05:13, Bertini, Denis Dr. <<a href="mailto:D.Bertini@gsi.de" class="">D.Bertini@gsi.de</a>> wrote:
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<div style="margin-top: 0px; margin-bottom: 0px;" class="">I am facing a problem when trying to write on a Lustre filesystem ( v 2.12) using standard fortran IO </div>
<div style="margin-top: 0px; margin-bottom: 0px;" class="">code ( compiled with GNU gfortran 8.3).<span style="font-size: 12pt;" class=""> </span></div>
<div style="margin-top: 0px; margin-bottom: 0px;" class="">The io rate sporadically goes extremely slow ( sometime down to 20/10 kBytes/s ! ) giving the</div>
<div style="margin-top: 0px; margin-bottom: 0px;" class="">feeling that the job is just hanging.</div>
<div style="margin-top: 0px; margin-bottom: 0px;" class="">Is this problem known by the community?</div>
<div style="margin-top: 0px; margin-bottom: 0px;" class="">Is there something a user should be aware when using Fortran IO together with</div>
<div style="margin-top: 0px; margin-bottom: 0px;" class="">the lustre filesystem?</div>
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<div style="margin-top: 0px; margin-bottom: 0px;" class="">The code (tarball in attachment) i am using is very simple and i would be grateful is somebody could <span style="font-size: 12pt;" class="">try it to see if this behaviour is a local or general problem.</span></div>
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<div>It's been 30 years since I did anything directly with Fortran, so I can't help you there, but I would suggest to debug this from the IO side with tracing. Use "strace" if a single-threaded program, or Darshan if a parallel program, or other related tools,
and you can get stats about IO size and alignment without having to understand the code first. This may surprise you if the application is doing e.g. 32-byte writes because you specified the array variables in the wrong order, or something.</div>
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<div>Cheers, Andreas</div>
<div>--</div>
<div>Andreas Dilger</div>
<div>Lustre Principal Architect</div>
<div>Whamcloud</div>
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