Bill, > Thanks...I'll just unthread it...How does netCDF get its speed. > Is the file in fact memory mapped after the create steps? NetCDF gets its speed from doing its own buffering and from handling arrays as arrays instead of as single values. The version we distribute is not memory mapped, although Glenn Davis did write a memory-mapped version available from the URL in this email: http://www.unidata.ucar.edu/glimpse/netcdf/2480 However, it didn't actually speed things up much and in some cases actually made the performance significantly worse than the standard buffered version. You could try it to see if it improves things ... --Russ _____________________________________________________________________ Russ Rew UCAR Unidata Program address@hidden http://www.unidata.ucar.edu