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I have an HP ProLiant DL160G6 server, with 2 CPU's and 48GB ram, with following modules:

  • 4x 8GB Module - DDR3 1066MHz (KTH-PL310Q8/8G)
  • 4x 4GB Module - DDR3 1333MHz (KTH-PL3138/4G)

I'm re-purposing the server now to be a VMWare host, and wonder what would be the fastest RAM configuration placement?

Also, will it make any sense to place faster memory (16 GB on 1333MHz) on 1st CPU, and slower on 2nd, despite it creating an non-even configuration (16 + 32)?

Otherwise, should I just place:

  • P1 - Channel 0 - 2x 8GB
  • P1 - Channel 1 - 2x 4GB
  • P2 - Channel 0 - 2x 8GB
  • P2 - Channel 1 - 2x 4GB
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2  
Are you sure it matters? Because traditionally RAM SPEED is not exactly a distinguishing factor for a virtualization host. THey normally are in this order: Disc IO, RAM Amount, CPU speed. As long as CPU speed is not a limiting factor (and interesting enuogh that is where the ram speed comes into play as it makes the CPU faster) it is a total non issue. –  TomTom Feb 4 at 11:29
    
You have a point, though I do would like to get the best performance I can. –  SyRenity Feb 4 at 11:33
    
Since you can put the same amount of RAM on each channel (12 GB), and perfectly balance both your CPUs and channels, why would you possibly not want to do that? –  David Schwartz Feb 4 at 13:23
    
After studying the subject deeper, it's indeed seems to be the only way. –  SyRenity Feb 4 at 16:37

1 Answer 1

up vote 11 down vote accepted

For an HP ProLiant DL160 G6, there are a few things to consider.

Summary:

  • Balance the DIMMs across CPUs.
  • Heaviest rank goes farthest from the CPU in each bank.
  • The presence of Quad-Rank memory will limit you to only using 12 of the 18 slots in the server.

So, your best option is for each CPU, populate Slots A and B with 8GB modules. Populate Slots C and D with 4GB modules.

The result will likely run at 800MHz instead of the native 1066MHz of the 8GB sticks or the 1333MHz of the 4GB sticks. If you remove two of the 4GB modules, the system will probably run at 1066MHz.


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Thanks for the very detailed answer! I'm always confused with the correct placement of RAM modules, and glad there are some experts here who already cut their teeth at this. Is there any way to see what the exact speed will be, so I could decide if I should put all 48 GB, or just 32? –  SyRenity Feb 4 at 15:46
    
Reading here, it seems that the difference in speed is actually very negligible: communities.vmware.com/thread/306073 –  SyRenity Feb 4 at 16:19
    
Also just to confirm, any sense taking NUMA into account here, or the different RAM size will not allow it? –  SyRenity Feb 4 at 16:22
    
I'm just trying to tell you how to arrange the RAM in the server. You really don't have any other options. –  ewwhite Feb 4 at 16:23
    
Clear, thanks for the helpful advice. –  SyRenity Feb 4 at 16:36

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