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    How many vCPUs can I have?

    IT Discussion
    hyper-v hyper-v 2016 vcpu virtualization hypervisor
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    • Reid CooperR
      Reid Cooper
      last edited by

      Ideally you want enough RAM to hold the database and any temporary or cache tables in RAM without having to touch the disk. More than that, and it is just wasted.

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      • JaredBuschJ
        JaredBusch @scottalanmiller
        last edited by

        @scottalanmiller said in How many VCPU’s can I have?:

        In a situation like this, I would not assign more than 19 vCPU across the workloads.

        What? This makes no sense.

        This implies that I can never have more than 19 virtual machines with 1 vCPU each.

        Unless all 19 are super busy this will never be a problem. When you sprawl to single purpose VMs, you will constantly have at least a few mostly idle VMs.

        scottalanmillerS 1 Reply Last reply Reply Quote 1
        • scottalanmillerS
          scottalanmiller @JaredBusch
          last edited by scottalanmiller

          @JaredBusch said in How many VCPU’s can I have?:

          @scottalanmiller said in How many VCPU’s can I have?:

          In a situation like this, I would not assign more than 19 vCPU across the workloads.

          What? This makes no sense.

          This implies that I can never have more than 19 virtual machines with 1 vCPU each.

          Unless all 19 are super busy this will never be a problem. When you sprawl to single purpose VMs, you will constantly have at least a few mostly idle VMs.

          No, in a situation like this there are only four VMs. It's the situation like this that causes the limit, not my use of only 19 threads.

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          • scottalanmillerS
            scottalanmiller
            last edited by

            Tags added. Title fixed.

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            • PhlipElderP
              PhlipElder @pchiodo
              last edited by

              @pchiodo said in How many vCPUs can I have?:

              @Obsolesce I have also found through experience that more memory on a SQL server does not necessarily improve performance. This is also true with VCPUs. I would monitor closely and change one thing at a time. Just my 2 pennies worth

              Concur. We do a lot of testing with VMFleet and other utilities with monitoring via Performance Monitor or Telegraf/Grafana.

              There is a sweet spot with so many variables coming into play. Disk subsystem being one key.

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              • wrx7mW
                wrx7m
                last edited by

                Conversely, I over-allocated vCPUs across several VMs (ESXi) when I was new to type 1 hypervisors and ran into performance issues associated with high CPU ready times. After scaling down, performance improved dramatically.

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