• The zlib library accepts a deflate factor of 0 through 9.
• NetCDF-4 does not allow a deflate setting of 0, it does not deflate the data, but does cause a performance penalty.
• We do not see much difference in compression by using higher numbers for the deflate factor, but there is certainly a performance penalty.
• Therefore we suggest that a deflate numer of 2 is a good choice. You may have different results.
• Compression cannot be used when writing data with parallel I/O. (It can be used when reading data with parallel I/O.)
• The HDF5 library also offers szlib compression, based on the szlib compression library. Since this library has some license restrictions (for commercial users creating datasets), we don't support creating szlib compressed data.

2009 Unidata NetCDF Workshop for Developers and Data Providers > Chunking and Deflating Data with NetCDF-4