Re: Value of Quad vs. Dual Processor machine

> On Tue, 11 Nov 2003, Rod Taylor wrote:
>
>> On Tue, 2003-11-11 at 18:32, Chris Field wrote:
>> > We are getting ready to spec out a new machine and are wondering about
>> > the wisdom of buying a quad versus a dual processor machine.  Seing as
>> > how postgres in not a threaded application, and this server will only
>> be
>> > used for log/transaction analysis (it will only ever have a few large
>> > queries running).  Is there any performance to be gained, and if so is
>> > it worth the large cost?  Any thoughts/experience are much
>> > appreciated...
>>
>> Since you're asking the question, I'll assume you don't have CPU
>> intensive queries or monstrous loads.
>>
>> I'd probably invest in a Quad system with 2 chips in it (2 empty
>> sockets) and put the difference in funds into a few extra GB of Ram or
>> improved IO.
>>
>> In 6 months or a year, if you start doing longer or more complex
>> queries, toss in the other 2 chips. So long as you don't hit a memory
>> limit, it'll be fine.
>
> Note that you want to carefully look at the difference in cost of the
> motherboard versus the CPUs.  It's often the motherboard that raises the
> cost, not the CPUs so much.  Although with Xeons, the CPUs are not cheap.
>
> The second issue is that Intel (and AMD probably) only guarantee proper
> performance from chips int he same batch, so you may wind up replacing the
> two working CPUs with two new ones to go with the other two you'll be
> buying, to make sure that they work together.
>
> My guess is that more CPUs aren't gonna help this problem a lot, so look
> more at fast RAM and lots of it, as well as a fast I/O subsystem.
>
> 2 CPUs should be plenty.
I agree that the additional cpus won't help as much since I haven't found
any benefits in terms of individual query speed for a quad vs. an smp on
benchmarks I've run on test machines I was considering purchasing.  Quads
are also expensive - on similar architectures the quad was 20k vs 7k for
the dual.
>
>
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