Implicit CPU/Memory Limits?

[Dan_I]

1. Without resource pools, for VMs that are setup with unlimited CPU and memory resources, memory will be implicitly limited by the amount in the "Hardware" tab of VM Properties, correct? CPU will be limited by the hardware CPU for the ESX host that the VM is running on?

2. With resource pools that span the cluster and those same VMs, would memory still be implicitly limited by the amount defined in the "Hardware" tab of VM Properties? CPU would now be limited by the CPU resources of the resource pool, correct? Not by the ESX host physical CPU sources...

Thanks in advance...

[weinstein5 · Accepted solution]

1. Without resource pools and limits set - you are correct - CPU will be limited to maximum speed (GHz) of a core for each virtual CPU of the VM because a virtual CPU can only run on a single core at a time -

2. With resource pools the vm memory is ultimately limited limited by the amount defined in the "Hardware" tab unless of the course the resource pool does not have enough memory available to fulfill that request. For CPU it is still limited by the number of cycles again is limited by the number of cycles a single core can provide - for example you have a resource pool with a limit of 20 GHz on a cluster with ESX Hosts running 3 GHz Quad Core processors and you have a single vCPU VM it will only get a maximum of 3 GHz because that vCPU can only run on a single core -

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[Dan_I]

Thanks for the response. Seems like bottom line the vCPU is limited by the physical CPU in the host servers.

Using the parameters of your example, suppose I have a VM with 2 procs, does that limit CPU resource use to 6000MHz implicitly with regard to the Resources TAB.

Thanks!

[weinstein5]

That is correct - and in regards to dual vCPU VM it will be 6000 MHz but split 3000 MHz per vCPU

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