Re: Memory speed question

I recommend benchmarking/testing

1. you can focus on a significant workload driver on your application and measure the effect on response time (end to end and per execution)
2. microbenchmark the memory itself - check out intel memory latency checker https://software.intel.com/en-us/articles/intelr-memory-latency-checker#whatdoesitmeasure

You can probably try that on one of the nodes first (analyze and correlate the numbers) then if everything is okay proceed with the rest.

This reminds me of the Exadata X2 days where going for the memory expansion kit drops the memory frequency to 800 MHz from 1333 MHz. The expansion kits are usually done on dev/test/qa environments so we could squeeze more databases on the cluster vs adding more nodes (pricier).

-Karl

On Fri, Mar 31, 2017 at 2:54 PM, Hameed, Amir <Amir.Hameed_at_xerox.com> wrote:

> 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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Karl Arao
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