On Thu, Sep 16, 2004 at 02:07:37PM -0700, Josh Berkus wrote:
> Jim,
> > What about benefits from putting WAL and pg_temp on seperate drives?
> > Specifically, we have a box with 8 drives, 2 in a mirror with the OS and
> > WAL and pg_temp; the rest in a raid10 with the database on it. Do you
> > think it would have been better to make one big raid10? What if it was
> > raid5? And what if it was only 6 drives total?
> OSDL's finding was that even with a large RAID array, it still benefits you to 
> have WAL on a seperate disk resource ... substantially, like 10% total 
> performance.    However, your setup doesn't get the full possible benefit, 
> since WAL is sharing the array with other resources.
Yes, but if a 3 drive raid array is 40% slower than a single disk it
seems like the 10% benefit for having WAL on a seperate drive would
still be a losing proposition.

BTW, my experience with our setup is that the raid10 is almost always
the IO bottleneck, and not the mirror with everything else on it.
Jim C. Nasby, Database Consultant               [EMAIL PROTECTED] 
Give your computer some brain candy! www.distributed.net Team #1828

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