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Patrick, > On the netcdf-3 vs netcdf-4 issue I can at the moment > only speculate. As a rule, reading small quantities of data > with netcdf-4 is always slower than netcdf-3 because the > underlying HDF5 file format is based on b-trees rather than the > linear disk layout of netcdf-3. Since vars reads a single > element at a time, that overhead can, I suspect, be significant. > I am, however surprised that it is as large as you show. In this case, no b-trees are involved, because the data storage is contiguous, not chunked (according to ncdump -h -s). So I'm surprised how slow the strided netCDF access is, and suspect there might be a performance bug in how netCDF-4 uses the HDF5 API for strided access. --Russ Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu Ticket Details =================== Ticket ID: ZFB-587742 Department: Support netCDF Priority: Normal Status: Closed