Re: pg_xlog question

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.

Testing the proper failover under load is recommended and you need to have a
journallig file system to make sure that the transaction logs are in sane
state. PG can not recover from corrupted transaction logs..

HTH

Bye
Shridhar

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