On Thursday 19 June 2008 18:10, Bill Moran wrote:
> In response to 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?
>
> No. If that happens you end up with corrupt disks. The chance of that
> going unnoticed by the OS is pretty slim.
>
> > 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?
>
> Sounds to me like there's something seriously wrong with you OS or your
> PostgreSQL install. What version of PostgreSQL is this? What OS?
>
> --
Centos 5 with the Posgres that comes with it - 8.1
regards
garry