[netcdfgroup] NF90_SYNC question

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: [netcdfgroup] NF90_SYNC question
• From: Leon Maurer <leon.maurer@xxxxxxxxx>
• Date: Wed, 20 Feb 2013 11:00:59 -0600

I've got a -- possibly ill posed -- question about the NF90_SYNC command:
does calling it append new data to the already existing file (in the same
way that a few more 'write(1,*)'s would) and modify a few existing things,
or does it rewrite the file from scratch? Does it do any/much reading in
the process?

I'm using a netCDF-4/HDF5 file with compression.

I'm using HTCondor <http://research.cs.wisc.edu/htcondor/>'s standard
universe, which effectively captures all file input/output and redirects it
over a network. Although my code only produces ~100MB of new data per day,
I'm told that the resulting network usage is dangerously high. The program
calls NF90_SYNC every 5 minutes, so I'm wondering if that could be
the culprit. (i.e. if it's doing a lot of reading/writing in the process.)

(Also, I just want to confirm that the NF90_SHARE flag doesn't work for
netCDF-4/HDF5 files. The NF90_SYNC
page<http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-f90/NF90_005fSYNC.html>
recommends using
the flag, but doesn't mention netCDF-4/HDF5file incompatibility; mentioning
the incompatibility is saved for the NF90_CREATE
page<http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-f90/NF90_005fCREATE.html>
.)

Thanks.
-Leon

• Follow-Ups:
  • Re: [netcdfgroup] NF90_SYNC question
    • From: Karsten Bolding
  • Re: [netcdfgroup] NF90_SYNC question
    • From: Russ Rew