Re: [Pytables-users] checksum always verified?

[Francesc A. <fa...@gm...>]

Yes, if the fletcher32 filter is used, it is always verified during 
reads.  I never experienced a failure myself, but a look at the code:

http://www.hdfgroup.org/ftp/HDF5/releases/hdf5-1.8.1/src/unpacked/src/H5Zfletcher32.c

is enough to see that this is the case.

Francesc

On 2/27/13 9:35 PM, Anthony Scopatz wrote:
> Sorry, I don't know.  I never have used this feature.   Maybe someone 
> who has can chime in.
>
>
> On Wed, Feb 27, 2013 at 2:26 PM, Frédéric Bastien <no...@no... 
> <mailto:no...@no...>> wrote:
>
>     That is fine with me. I just want to detect if my data got corrupted
>     by hardware problems.
>
>     Do someone know if it always get verified? Do you know if this cause
>     significant speed difference?
>
>     thanks
>
>     Frédéric
>
>     On Wed, Feb 27, 2013 at 3:21 PM, Anthony Scopatz
>     <sc...@gm... <mailto:sc...@gm...>> wrote:
>     > I think that the checksum is on the compressed data...
>     >
>     >
>     > On Wed, Feb 27, 2013 at 2:16 PM, Frédéric Bastien
>     <no...@no... <mailto:no...@no...>> wrote:
>     >>
>     >> Hi,
>     >>
>     >> we just got some problem with our file server and this bring me
>     >> question on how to detect corrupted files.
>     >>
>     >> There is a way to specify a filter when creating a table that add a
>     >> checksum[1].
>     >>
>     >> My questions is, when a file is created with checksum, are they
>     always
>     >> verified when the chunks are uncompressed? Can we specify when
>     we open
>     >> the file if we want to check it or not? The examples I found
>     only talk
>     >> about it when we create the file.
>     >>
>     >> thanks
>     >>
>     >> Frédéric Bastien
>     >>
>     >>
>     >> [1]
>     http://pytables.github.com/usersguide/libref/helper_classes.html
>     >>
>     >>
>     >>
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-- 
Francesc Alted