On Thursday 19 June 2008 18:52, Adrian Klaver wrote:
> -------------- Original message ----------------------
> From: Garry Saddington <garry(at)schoolteachers(dot)co(dot)uk>
>
> > On Thursday 19 June 2008 16:55, Joshua D. Drake wrote:
> > > On Thu, 2008-06-19 at 16:55 +0100, Garry Saddington wrote:
> > > > I have had a serious loss of data and wondered if anyone could shed
> > > > any light on what may have happened.
> > > > My users have been writing reports on students. No error messages
> > > > have been produced and when called back up the reports seem to be
> > > > present at the time of writing. However, next day they have
> > > > disappeared, and they do not appear in a pg_dump. They seem to have
> > > > been kept in memory and never written to disk.
> > > > We are using Zope and connecting to Postgres through psycopg on
> > > > Centos 5. I suspect a hard disk failure but any other ideas would be
> > > > welcome. Would these reports be in the WAL?
> > >
> > > If it was hardware related you would know, quickly. This sounds a great
> > > deal more like an application level interaction. Perhaps your zope
> > > application caches things for a while before committing to disk?
> >
> > Yes I thought of this but once the report is sent to the DB a separate
> > query is run to get all of that teacher's reports and these are then
> > displayed on a new page. They all appear here but then disappear later.
> > Zope has transaction machinery that rolls everything back on an error, so
> > Postgres must have indicated a successful write somehow. I read in a
> > Postgres manual that the hard disk may report to the OS that a write has
> > occured when it actually has not, is this possible? Oh, and the problem
> > has been intermittant. Another thing that happened this morning is that
> > Postgres had today as 18/06/2008 when in fact it was 19/06/2008 and the
> > OS reported this correctly. Restarting postgres sorted it, could this be
> > the problem?
> > Regards
> > Garry
>
> Seems like a transaction with no commit. Basically along as the session is
> active the data is there but once the session is closed the data does not
> persist.
>
Makes sense but what is to blame?
Regards
Garry