Re: Breaking the 2GB barrier?

"Thaden, John J" <ThadenJohnJ@xxxxxxxx> writes:

>    Any further news on when users will be able to create NetCDF files
> larger than 2GB?  I understand this is possible now under highly
> proscribed conditions but was informed that those conditions should
> dissolve soon, when a standard upon which NetCDF depends is updated.
> Thanks.
> -John Thaden
>
>

Howdy John!

The current release of netCDF (3.6.1) can create files considerably
larger than 2GB already.

In addition to the large files that can be created in netCDF classic
format (which have, as you note, many restrictions), there is also the
64-bit offset format, introduced in version 3.6.0, which can write
very large files without many restrictions.

For a complete discussion of the current large file capabilities of
netCDF, see:

http://www.unidata.ucar.edu/software/netcdf/docs/netcdf/Large-File-Support.html

Another possibility for large file creation is to use netCDF-4, which
can create files using HDF5. Since HDF5 does not have a 2GB size
problem, netCDF-4 users will not have a problem working with very
large files.

NetCDF-4 may be what you refer to waiting for another standard. It is
awaiting the (somewhat delayed) HDF 1.8.0 beta release. NetCDF-4 is
currently available in alpha release, but will not be available as a
full release for some time, and is not currently suitable for
operational use. A full release of HDF5 1.8.0 is required before
netCDF-4.0 can reach full operational status.

However, there's no need to wait for netCDF-4. The current
capabilities of netCDF allow for the use of very large files with
64-bit offset format. All you need to do is change the cmode flag in
your call to nc_create in order to create a 64-bit offset format
file. For more info, see:

http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-c/nc_005fcreate.html

Please let me know if this didn't answer your questions.

Thanks,

Ed

-- 
Ed Hartnett  -- ed@xxxxxxxxxxxxxxxx

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