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I know it's a common question but I need to ask anyway, just to clarify: How many cores should I assign to my kvm clients?

The host machine has 1 CPU with 8 cores. How many cores should I give the clients if..

  1. I have only one client
  2. I have two clients with equal load
  3. I have two clients with unequal load
  4. I have 8 clients
  5. I have more than 8 clients

My clients mostly run MongoDB+NodeJS, I think multithreading would be an advantage or not? The host cpu is from Intel, I have the hyperthreading (virtual) cores as well..

I'm happy for any experiences and advices, most of the threads concerning this questions end with "use 1 core per client" - but variation 1-3 would end with cores not used at all - or am I wrong

EDIT: I think I need to focus the question more:

  1. Is it a bad idea, to have more cores assigned to clients than the actual host has?
  2. Does more cores for a virtual machine mean more power?
  3. Needs the thread-change / (core change??) for a virtual machine more performance than running it as a single core?

This is not ressource planning - I'm grateful for some kvm advices here as I don't understand the affects in some situations.

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    Give them as many as they need. – Michael Hampton Feb 9 '17 at 22:51
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    But that's the question, what leads to the optimal usage of the host? – christian667 Feb 9 '17 at 23:20
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    Possible duplicate of Can you help me with my capacity planning? – yoonix Feb 9 '17 at 23:21
  • I don't need help with capacity planning, I hoped to get some advice by more experienced kvm admins. The sum of client cores should not be less the number of the (non virtual) host cores or is this wrong? – christian667 Feb 9 '17 at 23:29
  • Really, CPUs are probably the cheapest part of the whole setup. Who cares if you only utilize 80% of its capacity rather than 90%? Just give your guests what they need. – Michael Hampton Feb 9 '17 at 23:31

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