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[netCDF #KSJ-559079]: Netcdf 4 file format's general

> 1. If we used Netcdf4 format of file system, is it store larger
> amount of data than Netcdf3?
It is not easy to answer that question. I can think of
two factors that will affect the answer.

First, if fill is not used in either case, then netcdf-3 files
should be smaller than a corresponding
netcdf-4 file. If fill is enabled, then it may be the case that
the netcdf-4 file is smaller because, if memory serves, it can
avoid actuallyallocating space for the fill data until the data is
actually read.

Second, The record dimension (UNLIMITED) can affect the space used.
In netcdf-3, if many variables have a first unlimited dimension, and
the number of records has to grow for only a single variable, then
significant space can be allocated for the other variables as well.
The netcdf-4 format can avoid this.
 
>2. If we used Netcdf4, is it faster than Netcdf3 to write and read?
I am not sure of the answer. Perhaps other people here can comment. [Russ?].

>3. Does the Netcdf Java library used Netcdf C libarary to read file of Netcdf4
> file format? Is it faster way to read the file?
For reading, the Java library does not actually need to use the C library.
However Java is likely to be slower to some degree than the C library.
I should note that in the newest java library, netcdf-4 file writing
is possible and it uses the c-library to do that writing.




=Dennis Heimbigner
  Unidata


Ticket Details
===================
Ticket ID: KSJ-559079
Department: Support netCDF
Priority: Normal
Status: Closed