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From: Arjen van der Meijden <acmmailing@tweakers.net>
To: pgsql-performance@postgresql.org
Subject: Re: SSD options, small database, ZFS
Date: Fri, 18 Nov 2011 08:02:14 +0100
Message-ID: <4EC602F6.5030105@tweakers.net> (raw)
In-Reply-To: <F60C018B-9DCD-461A-A098-D9657A536698@morefoo.com>
References: <0464974E-CF82-41D7-A266-5BAE3CBCEC51@morefoo.com>
	<4E9811DE.6030601@tweakers.net>
	<F60C018B-9DCD-461A-A098-D9657A536698@morefoo.com>



On 18-11-2011 4:44 CSS wrote:
> Resurrecting this long-dormant thread...
>> Btw, the 5500 and 5600 Xeons are normally more efficient with a multiple of 6 ram-modules, so you may want to have a look at 24GB (6x4), 36GB (6x4+6x2) or 48GB (12x4 or 6x8) RAM.
>
> Thanks - I really had a hard time wrapping my head around the rules on populating the banks.  If I understand it correctly, this is due to the memory controller moving from the south(?)bridge to being integrated in the CPU.

That's not complete. A while back Intel introduced an integrated memory 
controller in the Xeon's (I think it was with the 5500). And doing so, 
they brought NUMA to the mainstream Xeons (Opterons had been doing that 
from the start).
The memory controllers in 5500/5600 are "triple channel". I.e. they can 
distribute their work over three memory channels at the same time. The 
next generation E5 Xeon's will have "quad channel", so it'll be going 
even faster with module count than.

With these kinds of cpu's its normally best to have increments of "num 
channels"*"num cpu" memory modules for optimal performance. I.e. with 
one "triple channel" cpu, you'd increment with three at the time, with 
two cpu's you'd go with six.

Having said that, it will work with many different amounts of memory 
modules, just at a (slight?) disadvantage compared to the optimal setting.

Best regards,

Arjen



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