On Tue, 21 Oct 2003, Markus Wollny wrote:
> Hi!
>
> > -----Ursprüngliche Nachricht-----
> > Von: Shridhar Daithankar [mailto:shridhar_daithankar@persistent.co.in]
> > Gesendet: Dienstag, 21. Oktober 2003 08:08
> > An: pgsql-general@postgresql.org
> > Betreff: Re: [GENERAL] Recomended FS
>
> > Can you compare ogbench results for the RAID and single IDE
> > disks? It would be
> > great if you could turn off write caching of individual
> > drives in RAID and
> > test it as well.
>
> One thing I can say from previous experiences is that the type of RAID
> does matter quite a lot. RAID5, even with a quite expensive Adaptec
> SCSI-hardware-controller, is not always the best solution for a
> database, particularly if there's a lot of INSERTs and UPDATEs going on.
> If you're not too dependant on raw storage size, your best bet is to use
> the space-consuming RAID0+1 instead; the reasoning behind this is
> probably that on RAID5 the controller has to calculate the parity-data
> for every write-access, on RAID0+1 it just mirrors and distributes the
> data, reducing overall load on the controller and making use of more
> spindles and two-channel-SCSI.
Theory vs. real life. In Theory, RAID5 is faster because less data have
to be written to disk. But it's true, many RAID5 controllers don't have
enough CPU power.
