Re: pg_xlog question

On 6 Aug 2003 at 12:52, Shridhar Daithankar wrote:

> On 6 Aug 2003 at 8:36, Mario Weilguni wrote:
>
> > Does anybody know if pg_xlog are essential for postgres to start? What would
> > happen if those files are lost, is the whole database corrupted or simply
> > some transactions lost?
> >
> > I want to know if the following cluster setup would work:
> > * /dbase - contains the database itself, is on a DRBD mirror device and spread
> > across 2 machines.
> > * /dbase/pg_xlog is a symlink to /pg_log and is a local partition, not a DRBD
> > device
> > * what would happen if a failover happens, and the pg_xlog on the other
> > machine is empty. will postgres simply recreate those files (maybe some tx
> > are lost) or cant this setup work correctly?
>
> I doubt. It might end up with some transaction uncommittied in files.
>
> If you could replicate/rsync pg_xlog to another machine, you could get it
> correctly in case of failover.

Argh.. I forgot.. Simple option is to sync the pg_xlog while doing failover. It
might add some 10 odd sec to failover process but should be bullet proof..

I don't know if PG is nose poking about permissions of those files. otheriwse
it might refuse to start.. Check out..

Worth adding to failover HOWTO. I doubt if one exists for postgresql.

Bye
Shridhar

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