[gpfsug-discuss] data integrity documentation

[Sven Oehme]

a trace during a mmfsck with the checksum parameters turned on would reveal
it.
the support team should be able to give you specific triggers to cut a
trace during checksum errors , this way the trace is cut when the issue
happens and then from the trace on server and client side one can extract
which card was used on each side.

sven

On Wed, Aug 2, 2017 at 2:53 PM Stijn De Weirdt <stijn.deweirdt at ugent.be>
wrote:

> hi steve,
>
> > The nsdChksum settings for none GNR/ESS based system is not officially
> > supported.    It will perform checksum on data transfer over the network
> > only and can be used to help debug data corruption when network is a
> > suspect.
> i'll take not officially supported over silent bitrot any day.
>
> >
> > Did any of those "Encountered XYZ checksum errors on network I/O to NSD
> > Client disk" warning messages resulted in disk been changed to "down"
> > state due to IO error?
> no.
>
>  If no disk IO error was reported in GPFS log,
> > that means data was retransmitted successfully on retry.
> we suspected as much. as sven already asked, mmfsck now reports clean
> filesystem.
> i have an ibdump of 2 involved nsds during the reported checksums, i'll
> have a closer look if i can spot these retries.
>
> >
> > As sven said, only GNR/ESS provids the full end to end data integrity.
> so with the silent network error, we have high probabilty that the data
> is corrupted.
>
> we are now looking for a test to find out what adapters are affected. we
> hoped that nsdperf with verify=on would tell us, but it doesn't.
>
> >
> > Steve Y. Xiao
> >
> >
> >
> >
> >
> >
> > _______________________________________________
> > gpfsug-discuss mailing list
> > gpfsug-discuss at spectrumscale.org
> > http://gpfsug.org/mailman/listinfo/gpfsug-discuss
> >
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