find max of cpu and Ram combination

[hongying dong]

TIm,
I got a question for you here. I think we can not add unlimited RAM and CPUs to a Linux box, so where to find this limitation instead of west too much hardware?
We tried to add 200 gb RAM and 20 CPUs to a Linux server, so we shutdown machine and then we can't reboot machine. so we can only add 128 gb RAM and stay with 12 CPUs that we used to have, we were fine in this RAM and CPU combinations.

so I wonder if there is any tips or statistics to find the max RAM and CPUs can work together? like how much RAM motherboad can support, what is number of CPUs best work with size of RAM.

Let me know if I asked too many questions.

Thanks,
Robin

[Tim...]

Hi.

Not really sure what you are asking. Are you talking physical or virtual?

Physical:

Now many sockets are there in the motherboard? What is the maximum cor count for the CPUs that fit into the sockets? What rating does the motherboard have. These are all dependent on the motherboard manufacturer and the age of the board. Nothing I can predict. Check your vendor.

As far as memory is concerned, 64-bit architecture allows you to address petabytes of memory, but it is unlikely you will have a motherboard that would allow you to fit or address that much. The rating is totally dependent on the chipset on the motherboard. Once again, check with the manufacturer.

Virtual:

It totally depends on the virtualization product you are using. You need to check with the vendor about the maximum values for their product. Just remember:

- Don't allocate more virtual memory than you have physical memory on the server. Over allocation of memory does different things depending on the virtualization product. Some will not let you do it. Some will allow it to happen, then let the physical server swap like crazy, making performance terrible.
- Don't allocate more virtual CPUs than you have physical CPUs. If you do the virtual CPUs will just fight over physical CPU resources, making the VM slower than if you allocated less.

Like I said, I don't really know what you are asking here. The question is so vague and ... strange...

Cheers

Tim...

[hongying dong]

Tim,
Thank you very much. According to your answer, I know where to look for my info here. I will find out machine info from OS guys and doc from manufacturer. we need to add RAM and CPUs on all nodes, over 20 of them.

Thank you very much,

Robin

[Tim...]

Hi.

OK. The manufacturer will know the limits for your kit. Normally, people like Dell and HP publish the maximum memory and version of the CPU that is supported.

Just be careful on the memory front. In some cases, adding more memory to servers makes the memory speed drop down, making the total efficiency of the system worse than it was before the memory upgrade. Check if alternate memory configurations cause speed step changes.

Cheers

Tim...