HDF and HDF-EOS Workshop VII September 23-25, 2003 Silver Spring, MD Source: http://hdfeos.org/workshops/ws07/presentations/Rew/Rew_netHDF-short.ppt

1. Plans for an Enhanced NetCDF-4
Interface to HDF5 Data
Russ Rew, UCAR Unidata Program
Mike Folk, NCSA/UIUC
Ed Hartnett, UCAR Unidata Program
Robert E. McGrath, NCSA/UIUC

2. What is NetCDF?
• Similarities with HDF5:
A scientific data model
A data access library and set of interfaces
A format for storing and accessing data
• Differences from HDF5:
Simpler, more widely used (currently)
Less powerful, less performance-oriented
• Current version: netCDF-3 is supported by
UCAR Unidata Program

3. NetCDF-4/HDF5 Goals
• Combine desirable characteristics of netCDF
and HDF5, while taking advantage of their
separate strengths:
Widespread use and simplicity of netCDF
Generality and performance of HDF5
• Preserve format and API compatibility for
netCDF users
• Demonstrate benefits of combination in
advanced Earth science modeling efforts

4. NetCDF-4 Features Enabled by HDF5
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•
•
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Large file support
Parallel I/O
Multiple dynamic dimensions
Packed data, compression
New data types
Dynamic schema modifications
Other possibilities: groups, Unicode, userdefined types, better coordinate support, …

5. Backward Compatibility
• Two kinds of compatibility:
API:
Extension of netCDF-3 API
Support existing netCDF-3 applications by
recompiling/relinking
Format:
Access to existing netCDF-3 data
Access to HDF5 files written through netCDF-4 interface
• Leverage C interface for other interfaces to
Fortran90, C++, Perl, Ruby, …
• Java interface must be developed separately

6. NetCDF-4 Architecture
netCDF-3
netCDFnetCDF-3
applications
applications
netCDF
netCDF
files
files
netCDF-4
HDF5 files
HDF5
files
netCDF-4
netCDFnetCDF-4
applications
applications
HDF5
HDF5
applications
applications
netCDF-3
Interface
netCDF-4
Library
HDF5 Library
• Supports access to netCDF files and HDF5 files
created through netCDF-4 interface

7. NCSA Contributions
• Overall design
• Dimension scales
To support shared dimensions
Addition to HDF5 data model
• Parallel I/O
Using Argonne/Northwestern work
Challenging performance goal

8. Acknowledgments and URL
• The netCDF-4/HDF5 project is funded by
the NASA AIST program
• Unidata is sponsored by the National
Science Foundation
• URL:
www.unidata.ucar.edu/packages/netcdf-4