On Tue, 11 May 2004, Bjoern Metzdorf wrote:

> Hi,
> I am curious if there are any real life production quad processor setups 
> running postgresql out there. Since postgresql lacks a proper 
> replication/cluster solution, we have to buy a bigger machine.
> Right now we are running on a dual 2.4 Xeon, 3 GB Ram and U160 SCSI 
> hardware-raid 10.
> Has anyone experiences with quad Xeon or quad Opteron setups? I am 
> looking at the appropriate boards from Tyan, which would be the only 
> option for us to buy such a beast. The 30k+ setups from Dell etc. don't 
> fit our budget.
> I am thinking of the following:
> Quad processor (xeon or opteron)
> 5 x SCSI 15K RPM for Raid 10 + spare drive
> 2 x IDE for system
> ICP-Vortex battery backed U320 Hardware Raid
> 4-8 GB Ram

Well, from what I've read elsewhere on the internet, it would seem the 
Opterons scale better to 4 CPUs than the basic Xeons do.  Of course, the 
exception to this is SGI's altix, which uses their own chipset and runs 
the itanium with very good memory bandwidth.

But, do you really need more CPU horsepower?

Are you I/O or CPU or memory or memory bandwidth bound?  If you're sitting 
at 99% idle, and iostat says your drives are only running at some small 
percentage of what you know they could, you might be memory or memory 
bandwidth limited.  Adding two more CPUs will not help with that 

If your I/O is saturated, then the answer may well be a better RAID 
array, with many more drives plugged into it.  Do you have any spare 
drives you can toss on the machine to see if that helps?  Sometimes going 
from 4 drives in a RAID 1+0 to 6 or 8 or more can give a big boost in 

In short, don't expect 4 CPUs to solve the problem if the problem isn't 
really the CPUs being maxed out.

Also, what type of load are you running?  Mostly read, mostly written, few 
connections handling lots of data, lots of connections each handling a 
little data, lots of transactions, etc...

If you are doing lots of writing, make SURE you have a controller that 
supports battery backed cache and is configured to write-back, not 

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