Re: [netcdf-hdf] what the heck is fletcher32 all about, anyway?

Elena Pourmal <epourmal@xxxxxxxxxxxx> writes:

> Ed,
>
> Here is some documentation on Fletcher32 
> http://www.hdfgroup.uiuc.edu/RFC/HDF5/ARCHIVE/H5checksum/
>
> This document describes the final design and implementation
>
> http://www.hdfgroup.uiuc.edu/RFC/HDF5/ARCHIVE/H5checksum/EDC_spec.htm
>
> Checksum is ON by default, i.e read operation will fail, but there is an API 
> that allows you to disable checksum and get data back.
>
> Elena
>

OK, thanks!

Is the following correct:

Turning on the fletcher32 checksum filter causes a 4 byte-checksum to
be written with each chunk.

(What happens to contiguous data?)

When reading data with fletcher32 checksum enabled, any corruption of
the chunk will cause the read operation to fail.

There is a significant performance penalty when reading checksummed
data.

Is this all correct?

Thanks!

Ed


-- 
Ed Hartnett  -- ed@xxxxxxxxxxxxxxxx