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Re: CDF vs HDF [message #38862 is a reply to message #38854]

Tue, 30 March 2004 14:53

K. Bowman
Messages: 330
Registered: May 2000

Senior Member

In article <87ptaum3hk.fsf@lumen.indyrad.iupui.edu>,
mmiller3@iupui.edu (Michael A. Miller) wrote:

> NetCDF cannot handle files larger
> than 2 Gbytes due to an internal 32 bit integer.

This is not strictly true.

From the UNIDATA netCDF FAQ:

> Is it possible to create netCDF files larger than 2 Gbytes?
>
> It is possible to write netCDF files that exceed 2 Gbytes on platforms that
> have "Large File Support" (LFS). Such files would be platform-independent to
> other LFS platforms, but if you open such a file on an older platform
> without LFS, you would expect a "file too large" error.
>
> There are significant restrictions on the structure of large netCDF files
> that result from the 32-bit relative offsets that are part of the netCDF
> file format. If you don't use the unlimited dimension, only one variable can
> exceed 2 Gbytes in size, but it can be as large as the underlying file
> system permits. It must be the last variable in the dataset, and the offset
> to the beginning of this variable must be less than about 2 Gbytes. If you
> use the unlimited dimension, any number of record variables may exceed 2
> Gbytes in size, as long as the offset of the start of each record variable
> within a record is less than about 2 Gbytes. For examples of both these
> forms of large netCDF files, see the Large File Support section in the
> User's Guide.
>
> To enable LFS for writing large netCDF files requires that the libraries be
> built with specific combinations of platform-specific compile flags on some
> systems. For examples, see the Installation instructions.

OSes with LFS include IRIX, Solaris, AIX, ...

I have not tried this from IDL. We have a mixture of 32- and 64-bit
systems, and I need files to be portable.

Ken Bowman

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[Message index]

		Re: CDF vs HDF By: giglio on Thu, 01 April 2004 10:58
		Re: CDF vs HDF By: david.b.han on Thu, 01 April 2004 05:10
		Re: CDF vs HDF By: david.b.han on Thu, 01 April 2004 04:56
		Re: CDF vs HDF By: K. Bowman on Wed, 31 March 2004 08:20
		Re: CDF vs HDF By: mmiller3 on Wed, 31 March 2004 06:30
		Re: CDF vs HDF By: K. Bowman on Tue, 30 March 2004 14:53
		Re: CDF vs HDF By: mmiller3 on Tue, 30 March 2004 13:25
		Re: CDF vs HDF By: Paul Van Delst[1] on Tue, 30 March 2004 13:03

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