Re: Memory speed question

"Your mileage will vary" and "it depends" are always 100% accurate, but that does not make them useful.

Its generally correct to advise testing, but benchmarking memory access is a big task, and anyone holding a title like "architect" should expect to substantiate.

On 3/31/17 13:52, Dimensional DBA wrote:
>
> The information about going from 1600MHZ to 1066MHZ is in the Intel
> and HW documentation relative to Intel architecture.
>
> I have benchmarked systems with a variety of different applications
> java, python, perl, databases etc.
>
> The �your milage will vary� is of course very accurate. The
> performance differential to the app in some cases was very low and in
> other cases was up to 40% differential.
>
> Depends on your app and what the app is doing.
>
> *Matthew Parker*
>
> *Chief Technologist*
>
> *Dimensional DBA*
>
> *425-891-7934 (cell)*
>
> *D&B *047931344**
>
> *CAGE *7J5S7**
>
> *Dimensional.dba_at_comcast.net <mailto:Dimensional.dba_at_comcast.net>*
>
> *View Matthew Parker's profile on LinkedIn*
> <http://www.linkedin.com/pub/matthew-parker/6/51b/944/>
>
> www.dimensionaldba.com <http://www.dimensionaldba.com/>
>
> *From:*Tim Gorman [mailto:tim.evdbt_at_gmail.com]
> *Sent:* Friday, March 31, 2017 12:33 PM
> *To:* Amir.Hameed_at_xerox.com; Dimensional DBA; 'ORACLE-L'
> *Subject:* Re: Memory speed question
>
> Amir,
>
> I'd recommend pushing hard for concrete information: a KB or support
> documentation from Cisco. Lacking substantiation, it's just an opinion.
>
> Don't allow hearsay, opinions, and myths to propagate without
> challenge. Be respectful, be polite, but be firm.
>
> Hope this helps...
>
> -Tim
>
>
> On 3/31/17 13:08, Hameed, Amir wrote:
>
> For that we will need to buy memory and then add it to the host
> which is what we are trying to avoid. We have also asked our data
> center to check with Cisco and the response we got was that
> �mileage will vary�.
>
> *From:* Dimensional DBA [mailto:dimensional.dba_at_comcast.net]
> *Sent:* Friday, March 31, 2017 3:01 PM
> *To:* Hameed, Amir <Amir.Hameed_at_xerox.com>
> <mailto:Amir.Hameed_at_xerox.com>; 'ORACLE-L'
> <oracle-l_at_freelists.org> <mailto:oracle-l_at_freelists.org>
> *Subject:* RE: Memory speed question
>
> It is simplest to run a benchmark and you will see that your app
> will notice a difference if you have a low latency app.
>
> It also limits the overall amount of work that can be accomplished
> on that blade.
>
> *Matthew Parker*
>
> *Chief Technologist*
>
> *Dimensional DBA*
>
> *425-891-7934 (cell)*
>
> *D&B *047931344
>
> *CAGE *7J5S7
>
> *Dimensional.dba_at_comcast.net <mailto:Dimensional.dba_at_comcast.net>*
>
> *View Matthew Parker's profile on LinkedIn*
> <http://www.linkedin.com/pub/matthew-parker/6/51b/944/>
>
> www.dimensionaldba.com <http://www.dimensionaldba.com/>
>
> *From:*oracle-l-bounce_at_freelists.org
> <mailto:oracle-l-bounce_at_freelists.org>
> [mailto:oracle-l-bounce_at_freelists.org] *On Behalf Of *Hameed, Amir
> *Sent:* Friday, March 31, 2017 11:55 AM
> *To:* 'ORACLE-L'
> *Subject:* Memory speed question
>
> We have a four-node ESX farm/cluster where each node is loaded
> with 512G of physical memory. These ESX nodes are Cisco UCS
> blades. We are looking into adding more memory to each of these
> ESX hosts to increase the footprint to 750G/node. One of the data
> center architects had informed us last year that per Cisco, the
> sweet-spot of memory footprint on these blades is 512GB, after
> that the memory access speed would drop from 1600MHZ to 1066MHZ (a
> drop of ~ 30%). Because all of our VMs host application tiers and
> they run a lot of JVM processes, we are concerned that a drop of
> 30% will negatively impact our applications� performance. However,
> our data center has been telling us that the drop will not be
> noticed by the application which I find hard to believe. We also
> do not want to add another ESX host because of licensing cost.
>
> I was wondering if anyone is running their ESX hosts with memory
> over 512G/host and if they observed any issue with memory speed.
>
> Thank you,
>
> Amir
>

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