[netCDF #NOJ-562667]: NetCDF Performance

Lee,

When I run this on my SPARCstation, the output is:

 $ ./timeit
  Starting data initialization.
 Array sizes =  25MB.   Clock resolution =  0.001 ms.
 
 Time for   25MB           binary write =      0 msec.   
 Time for   25MB 10 binary rewind/writes =     0 msec.   
 Time for   25MB  8  binary file writes =      0 msec.   
 Time for   25MB          netcdf write =       0 msec.   Spd ratio =  1.05
 Time for   25MB 10 repeated netcdf write      0 msec.   Spd ratio =  2.26
 Time for   25MB  8 netcdf file writes =       0 msec.   Spd ratio =  2.34

The "0 msec." times are a symptom that something is not right, maybe the 
program should be using nanoseconds instead of milliseconds for this.  Also, 
I'm not sure how valid these times are, since a write may return immediately on 
Unix systems, since the write doesn't actually take place until the system 
buffers are flushed to disk, every 30 seconds or so, unless you actually do a 
close or explicit flush.  I/O benchmarks like this can be difficult to 
interpret unless you know how the system is dealing with buffering and caching. 
 I know almost nothing about how Fortran-90 I/O works on Unix systems, so take 
this with a little skepticism ...

--Russ


Russ Rew                                         UCAR Unidata Program
address@hidden                     http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: NOJ-562667
Department: Support netCDF
Priority: Normal
Status: Closed