On Thursday 19 June 2008 18:10, Bill Moran wrote: > In response to 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? > > 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
