On Tue, Nov 24, 2009 at 09:42:08AM -0500, Matthew Jones wrote:You lost the contents of one file didn't you? Hits on memory from
> Memory tests were run and no problems were reported. With MonetDB+bad
> memory I would expect to lose some data and no data was lost here.
cosmic rays cause random single bit flips at a small but measurable
rate--though ECC memory should help. These could cause something in
Linux's page buffer to go awry and hence ending up with an empty file
when unexpected. The bug rate of normal software means that that
these sorts of errors are almost completely masked, however when code
matures these sorts of errors start to become important. I'm not sure
if Monet is stable enough to think about this yet, but if you've got a
stable access pattern that only hits exactly the same code paths then it
shouldn't matter about the remaining bugs.
Higher assurance software tends to include checksums and other simple
invariants that are checked at various places in code to make sure that
errors like this aren't propagated too far.
--
Sam http://samason.me.uk/
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