Re: [netcdfgroup] NetCDF4 format and SZIP

• To: "Pascoe\, Stephen \(STFC\,RAL\,SSTD\)" <stephen.pascoe@xxxxxxxxxx>
• Subject: Re: [netcdfgroup] NetCDF4 format and SZIP
• From: Ed Hartnett <ed@xxxxxxxxxxxxxxxx>
• Date: Mon, 07 Sep 2009 10:24:41 -0600

"Pascoe, Stephen (STFC,RAL,SSTD)" <stephen.pascoe@xxxxxxxxxx> writes:

> I'd like to clarify how using HDF5 with SZIP support affects the files
> created by the NetCDF4 library.
>  
> According to the NetCDF4 INSTALL file you can optionally use HDF5+SZIP
> when building NetCDF4.  This implies that either SZIP-compressed NetCDF4
> is byte-compatible with ZIP-compressed NetCDF4 or that there are 2
> incompatible compressed NetCDF4 formats (ZIP and SZIP).  Can you confirm
> it is the former?

It's simple.

NetCDF-4 cannot create SZIP compressed HDF5 files.

But it is possible to read some HDF5 files with netCDF-4, even though
they were not created with netCDF-4. (This capability will expand with
the 4.1 release, which will read any HDF5 file that does not use
references, circular group structures, or a few other HDF5 features that
are not supported in netCDF).

So the point of building HDF5 with SZIP is to allow these szip
compressed files to be read by netCDF-4. This is a read-only capability.

> Assuming it is the former, what is the advantage of using SZIP?  Is SZIP
> automatically used if the HDF5 library has it?
>  
> Thanks,
> Stephen.
>  

Fans of szip say it gives better compression.

Thanks,

Ed

-- 
Ed Hartnett  -- ed@xxxxxxxxxxxxxxxx

• Follow-Ups:
  • Re: [netcdfgroup] NetCDF4 format and SZIP
    • From: Pascoe, Stephen (STFC,RAL,SSTD)
  • Re: [netcdfgroup] NetCDF4 format and SZIP
    • From: Ted Mansell

• References:
  • [netcdfgroup] NetCDF4 format and SZIP
    • From: Pascoe, Stephen (STFC,RAL,SSTD)