[Zope] Corrupted data.fs

[Tim Peters]

[Marco Bizzarri]
> We're experiencing nightly corruption of a Data.fs in an intranet
> application.
>
> We've removed all the packing/backup stuff, we've moved from zope 2.6.4
> to zope 2.7.4, but we still have data corruption in the morning.
>
> Here is the error from the event log:
...
> error: unpack str size does not match format
...
> CorruptedDataError:
> ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@

Note that those are the two symptoms described here, under
"FileStorage corruption":

    http://zope.org/Wikis/ZODB/FileStorageBackup

> I'm quite confident the problem is outside of Zope, but I would like to
> have some pointer on where to investigate in order to undestand the problem.

All we know about those is explained on the page referenced above. 
Best advice is to try running on different hardware.  If that makes
the problem go away (historically likely), running HW and I/O
diagnostic/stress tests appropriate for your HW and OS may identify
the failing component(s).  The most recent of these I know of where
the cause was definitely found turned out to be a RAID controller that
failed only under high load (but normally worked fine, making the
problem extra-hard to find).

If you determine a cause, please let us know what it was.