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Date:      Thu, 5 Oct 2006 12:26:00 -0700
From:      Chuck Swiger <>
To:        Paul Lathrop <>
Subject:   Re: PAE tuning
Message-ID:  <>
In-Reply-To: <>
References:  <> <> <>

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On Oct 5, 2006, at 12:13 PM, Paul Lathrop wrote:
>> You're supposed to tune the appropriate values considering the  
>> workload
>> the machine is going to handle.  "man tuning" has some additional
>> information, but without describing what kind of tasks you plan to do
>> with this machine with 14GB of RAM, nobody is going to be able to
>> provide you with really specific advice...
> Good point. :-)
> I intend to deploy this system as a database server running Postgresql
> 8.1. The database is huge (30-40Gb) and can easily grow (it has  
> gone as
> high as 100Gb). I expect as many as 1000 concurrent database  
> connections
> now, and a potential need for scaling this up later.

You should tune the network stack settings towards LAN use (shorter  
timeouts, larger send & receive buffers); you should probably tune  
down the # of vnodes, adjust SysV shared memory as Postgres recommends:

> I'm aware of the SystemV memory tuning issues related to running
> Postgres on FreeBSD and I'll address those as soon as I can get the
> system to see the RAM.
> I tried just installing the stock PAE kernel, but the system still
> doesn't even acknowledge the RAM above 4Gb. Is this because I have not
> yet performed the tuning?

Update your BIOS and then check the settings; there may be an option  
explicitly for PAE, or you might find that tweaking something like  
"PCI memory reservation", "4GB memory hole", or "MTRR mapping"  
between the options will help make the extra memory appear.


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