Heiko,
Thanks for pointing out the documentation problem and suggesting a fix.
We'll get the fix in soon.
--Russ
> Hi,
>
> the netcdf user guide describes the new chunking possibilities in
> http://www.unidata.ucar.edu/software/netcdf/docs/netcdf.html#Default-Chunking
>
> I think the paragraf:
>
> 'For unlimited dimensions, a chunk size of one is always used. Users are
> advised to set chunk sizes for large data sets with one or more
> unlimited dimensions, since a chunk size of one is quite inefficient.'
>
> is very misleading, and opposed to 'In particular, the idea of using 1
> for the chunksize of an unlimited dimension works well if the data are
> being read a record at a time. Any other read access patterns will
> result in slower performance.'
>
>
> In netcdf-3, it was usual to use a record-base read access pattern when
> an unlimited dimension was found. Advising users now to change the chunk
> size of the unlimited dimension to something different than 1 is in most
> cases wrong and will give slower performance. I suggest a sentence like:
>
> 'For unlimited dimensions, a chunk size of one is always used. For large
> datasets, where the size of limited dimensions is small compared to the
> unlimited dimensions, users are advised to avoid unlimited dimensions or
> to increase the chunk sizes of the unlimited dimensions. Be aware that
> an unlimited dimension with chunksize != 1 will result in slower
> performance for record-oriented access patterns which where common in
> netcdf-3.'
>
>
> Best regards,
>
> Heiko
>
> --
> Dr. Heiko Klein Tel. + 47 22 96 32 58
> Development Section / IT Department Fax. + 47 22 69 63 55
> Norwegian Meteorological Institute http://www.met.no
> P.O. Box 43 Blindern 0313 Oslo NORWAY
>
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