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Resource Allocation Rule of Thumb

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  • Resource Allocation Rule of Thumb

    I was wondering about a general rule of thumb for resource allocation.

    What I mean by this, is if you have a host with 'X' cores & 'Y' RAM, how many VM's worth of 'A' cores & 'B' RAM would you deploy?

    A lot of people over allocate resources, and am just wondering what the general rule of thumb for this would be.

  • #2
    Re: Resource Allocation Rule of Thumb

    Seems like this is a bit of a "How long is a piece of string" question. If the VMs are just idling, I'd say you could over commit them indefinitely. I've never heard of a general rule or ratio for over committing resources.
    Wesley David
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    • #3
      Re: Resource Allocation Rule of Thumb

      The thing to remember is resource allocation is dynamic; you can change it as when necessary

      Start off with 1 vCPU for EVERY virtual machine you create (unless OS or software require more). This article explains some of the reasons why you should use 1 vCPU and not load the VM up:

      It's ok to over allocate on memory as mentioned before. When the VM is up and running check on the Resource Allocation tab of the VM. This can tell you if you need to make amendments to allocations. Keep an eye on the Ballooned figure; if you start to see large amounts of ballooning then this can be down to paging faults. Also keep an eye on the Swapped figure.

      Be careful using shares, only use these if you are experiencing resource constraints.