Re: 2 x quad core or 4 x dual core? - server sizing

On Tue, Jan 11, 2011 at 11:49 AM, Martin Berg <[email protected]> wrote:
> On 01/11/2011 11:12 AM, Rafa Griman wrote:
>> Hi :)
>>
>> On Tue, Jan 11, 2011 at 10:56 AM, Martin Berg <[email protected]> wrote:
>>
>>> I've thought of this - but only one of my customers have tried this and it
>>> did not perform as
>>> expected (each core not being as fast as cores from the quad cores).
>>> The performance was so bad that they scrapped the server.
>>> I didn't have an opportunity to examine this (the problem might not have
>>> anything to do
>>> with the CPU's) - and I'm just being cautious.
>>>
>>
>> Could be a problem due to CPU-Memory bandwidth. The "problem" with
>> having many cores is that the bandwidth per core decreases as you
>> increase the number of cores per socket so apps that require a big
>> CPU-memory bandwidth will be affected.
>>
>> Depending on the DB, you can hit this issue. In the cases in which you
>> hit this issue, you can deactivate some cores at the BIOS. Usually
>> helps. Another options is to pin certain processes to certain cores
>> (cpusets, ...) leaving some other cores free for the OS and whatever
>> it has to do (logs, network, ...).
>>
>> Summarizing: having many cores/sockets is not always good ;) Depends
>> on your app, workflow, ...
>>
>> HTH
>>
>>    Rafa
>>
>
> This was an only-Oracle Database server, so leaving certain cores for
> other activities
> would probably not help a lot - and the whole idea of having as many
> cores as can be
> fitted into the Oracle license is somewhat negated by disabling some of
> the cores;-)


I know. I was just suggesting this in case you already have the server
and don't want to scrap it ;) As someone else mentioned 6 core/socket
servers.


> Following this line of thought: some years ago I visited a customer that
> had just bought a
> 16-CPU SUN (> $2M) to run their non-Oracle database after having spend 2
> years in not
> getting sufficient performance on an Intel server.
> They had not seen the performance improvements as they expected and
> after further
> investigation the database vendor came back and adviced to disable of
> some of the CPU's.
> The customer became so frustrated that they threw the previous database
> out and tried
> Oracle instead (which worked).


I talked with a potential customer once that was running Oracle on a
Sun server with 128 cores. 1/2 of those cores were completely idle ...
he was also frustrated ;)


> And: sticking certain processes to certain cores requires an OS (hint,
> hint ... :-)


I know, I assume you're running Oracle on an OS ... maybe SLES? ... ;)


> Anyway thanks for the suggestions.

   Rafa
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