On 2 Feb 2004 at 16:45, scott.marlowe wrote:

> Do you have the cache set to write back or write through?  Write through 
> can be a performance killer.  But I don't think your RAID is the problem, 
> it looks to me like postgresql is doing a lot of I/O.  When you run top, 
> do the postgresql processes show a lot of D status? That's usually waiting 
> on I/O

Actually I'm not sure.  It's setup with the factory defaults from IBM.  Actually when 
start hitting the limit I was surprised to find only a few D status indicators.  Most 
of the 
processes where sleeping.

> what you want to do is get the machine to a point where the kernel cache 
> is about twice the size or larger, than the shared_buffers.  I'd start at 
> 10000 shared buffers and 4096 sort mem and see what happens.  If you've 
> still got >2 gig kernel cache at that point, then increase both a bit (2x 
> or so) and see how much kernel cache you've got.  If your kernel cache 
> stays above 1Gig, and the machine is running faster, you're doing pretty 
> good.

I've set  shared to 10000 and sort to 4096.  I just have to wait until the afternoon 
before I see system load start to max out.  Thanks for the tips I'm crossing my 

Kevin Barnard

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