Re: Datatypes and performance

On Mon, Jul 07, 2003 at 01:30:09PM +0200, Mattias Kregert wrote:

> In the case of disk failure, the files will probably be damaged anyway and
> then i'll have to install new hardware or format+check badblocks and then
> restore from the backup. I can't see how fsync would help in the case of
> disk crash. Without reliable raid or something i think this would be a
> catastrophic failure => get new hardware: disk/ram/computer/building
> whatever and go find the (remote) backup.

True, it doesn't help with one disk, but RAID does work.

> In the case of power failure, you'll *might* have to restore from backup
> unless you use ReiserFS or some other journalling filesystem. I use
> ReiserFS. I also have a UPS installed, just to be sure...

> Journalling FS will fix the FS problems, so the files are ok.
> PG journal will fix the PG problems so the tables will be ok.

Firstly, journalling filesystems insure the integrity of the *filesystem*,
not the files on it. So your files can still be corrupted. You could enable
full data journalling. I would imagine that would cost you more than just
enabling fsync.

Secondly, IIRC the fsync applies to the PG journals, so turning off fsync
will kill the tables in a crash.

Basically, do you care about your data?

--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> "the West won the world not by the superiority of its ideas or values or
> religion but rather by its superiority in applying organized violence.
> Westerners often forget this fact, non-Westerners never do."
>   - Samuel P. Huntington