On Thursday 19 June 2008 18:52, Adrian Klaver wrote: > -------------- Original message ---------------------- > From: Garry Saddington <garry@xxxxxxxxxxxxxxxxxxxx> > > > 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
