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A request for a server (HP DL 160 Gen9) with 2 processors came through with a weird RAM configuration request today. They requested 2 8GB DIMMs and 1 16GB DIMM. Are there any numbers out there which would let me provide information on the performance issues they may experience from this? I imagine they will put the 2 GB DIMMS with one channel and the 16GB on another.

I've always heard to balance channel utilization and stick to the same size/type of RAM, is this a concern/does anyone have numbers on the performance hit this would cause (if any)? It seems strange to want 3 modules for 2 processors with 2 sizes of RAM chips.

Let me know if more information is required!

  • What? Who? When? – joeqwerty May 11 '15 at 22:19
  • Added more information. @joeqwerty What: A Server? Who: Not relevant. When: Today? I'm not certain what information you're looking for. Could some also explain why they downvoted? – Abraxas May 11 '15 at 22:22
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    Probably because your questions are almost certainly answered in the product manual. – yoonix May 11 '15 at 22:24
  • @yoonix it's not, hence asking. "Install DIMMs only if the corresponding processor is installed. "If only one processor is installed in a two processor system, only half of the DIMM slots are available. To maximize performance, it is recommended to balance the total memory capacity between all installed processors and load the channels similarly whenever possible. When two processors are installed, balance the DIMMs across the two processors" My question is how bad is this configuration. It seems weird to have 3 chips on 2 processors. – Abraxas May 11 '15 at 22:27
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    Some people downvote to get a badge. I upvoted you :) – Konrad Gajewski May 12 '15 at 9:31
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Why wouldn't you just correct the order? There's no reason to "what if" when you KNOW that this is not a recommended configuration. As for whether it will work, you will see once the server completes its POST.

But I don't think it's necessary to play that game.

Do you want to do this the right way?

If so, spec and arrange the RAM according to the DIMM population guidelines listed in the manual and below:

General Memory Population Rules and Guidelines:

  • Install DIMMs only if the corresponding processor is installed.
  • If only one processor is installed in a two processor system, only half of the DIMM slots are available.
  • To maximize performance, it is recommended to balance the total memory capacity between all installed processors and load the channels similarly whenever possible.
  • When two processors are installed, balance the DIMMs across the two processors
  • Place the DIMMs with the highest number of ranks in the white slot when mixing DIMMs of different ranks on the same channel.
  • Do not mix RDIMMs or LRDIMMs.
  • Quad rank RDIMMs are not supported in HP ProLiant DL160 Gen9 servers
  • Quad rank LRDIMMs are capable of up to two DIMMs per channel.
  • DIMMs of different speeds may be mixed in any order; the server will select a common optimal speed.
  • The maximum memory speed is a function of the memory type, memory configuration, and processor model.
  • The maximum memory capacity is a function of the memory type and number of installed processors.
  • To realize the performance memory capabilities listed in this document, HP SmartMemory is required
  • Thanks - I did tell them that it wasn't recommended and I wasn't sure if it would work and/or what the performance cost would be. They said that it was the config they were given and they aren't going to change it. I was hoping to find some information which had some comparisons of bad configs vs normalized configs of memory to hand off to them in case of any future issues. Thanks for the quotes from product bulletin/quickspecs I forwarded that on to them as well. – Abraxas May 11 '15 at 22:54
  • For the impact, I think it depends on what your systems are doing. But again, I can't understand why your team would willingly use a bad configuration. – ewwhite May 11 '15 at 22:55
  • Me neither -___- Thanks for your time. – Abraxas May 11 '15 at 22:56

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