DL580 G7 Ram Configuration Question

[ArcticWolf_11]

Hello, thinking about getting a DL580 G7 with 4x E7-4870s. My workload needs the fastest ram speed possible and according to this

http://h20564.www2.hpe.com/hpsc/doc/public/display?docId=emr_na-c02283239 

*If initial memory target is 64GB then populate a 4 processor system with eight cartridges of 4 - 2GB DIMMs each for a total of 32 DIMMs. Your maximum expansion target is 128GB with 64 2GB DIMMs.*

Does that mean that if I put say 32x1GB sticks in, will it be at max speed or would 64x1GB be needed to achieve max speed? Aside from future expansion, please tell me if this is at all remotely right as I am confused as how to configure the ram and how many sticks to buy to achieve maximum ram speed. Thanks

[TTr]

Examples 1 (optimal hemisphere) and 2 (improved hemisphere) in the URL you attached, would be the memory configurations to use. 

Example1 is offers the maximum performance, example 2 offers the second maximum performance. There is no mention of what the difference in the performance between the two examples is, but I would expect not to be significant. But I would expect the difference in the performance to be significant if you go with any of the other examples 3 - 6. The memory modules is "unbalanced" in those.

If you start with example 2, (initial target) you can upgrade to example 1 (maximum expansion target) by adding memory. You add exactly whatever you have installed to double up the memory without throwing out the initial memory.

If you start with example 1, you have to replace ALL the memory if you want increase capacity. Anything else, not replacing all of the modules, or using different capacity modules would lead to examples 3 -6 and performance degradation.

[ArcticWolf_11]

Alright, thanks. I think ill go and get 32x2GB sticks with it then. Also say that I do upgrade later on to 128GB, do I have to buy the same brand 32 sticks or could I go and get a different brand and or different capacity?

[Erdogan Temur]

Hİ @ArcticWolf_11

You can use HPE DDR3 Server Memory Configurator tool.

https://h22195.www2.hpe.com/MemoryTool/Home/SelectServer

[TTr]

> ...upgrade later on to 128GB

I would "stick" with 2GB sticks in the upgrade. If you want more than 128GB and buy higher capacity memory modules, you can shufle them around and keep the same modules withing the same CPU memory banks. i.e you can move the 32 sticks to 2 CPU banks and install higher capacity sticks to the remaining CPU banks.

[ArcticWolf_11]

Alright thanks all! Now when I click maximum performance and when I enter 64GB, why is it that it suggests 16x4GB in slot 1 and slot 8 of cartridges 1-8. Wouldn't 32x2GB be faster than that, slots 1, 3, 6, 8? Am I missing something here or will 16 sticks give me the most performance?

[TTr]

You get three options as the result for the memory configuration.  Option 3 is the best optimal one with 2GB modules spread evenly across ALL four channels

The other two options utilize higher density modules but only use two channels. This is acceptable but there is a significant performance penalty because CPUs 1 and 2 have no memory in their cartridge slots and have to cross over to the other cartridges to access memory.

Take a look at https://www.hpe.com/h20195/V2/getpdf.aspx/c04128284.pdf?ver=45

page 40, 41.

[ArcticWolf_11]

Oh I see, so if I want the most performance I would need to use 32x2GB, 4 sticks in each cartridge? So 64 sticks won't offer much if any more of a performance increase due to it already being in quad channel?

[TTr]

There is some performance gain going from 32 DIMMs (example 2 page 40) to 64 DIMMs (example 1 page 40) but it is not as huge as going from a non-balanced DIMM population (examples 6, 5, 4, 3) to 32 or 64 identical DIMMs. Also read the first and second bullet on page 41.