How the AHV allocate memory to VM | Nutanix Community
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Hi all

I just want to know how nutanix AHV allocate resource(cpu or memory) to VMs?

Like VMware resource share or limit, and memory overcommit?

You need to set CPU and memory to VM idividually. If you over assign(more then) your cluster can handle. Error will be thrown.

There is no memory oversubscription in AHV in the current versions.

There is no memory oversubscription in AHV in the current versions.

So how much CPU and memory are set, how much will the host consume? Not the actual usage of VM?

The VM will be consuming the actual current usage of CPU and memory. 

For example, if you create a VM with 16Gb of memory and at this point of time, the usage is 4Gb, it is consuming 4Gb from the host. But you will not be able to provision more than the host’s maximum of memory.

@Sergei Ivanov

Thank you for your reply

I have a node with 187.49GB of memory on it, there are three VMs , which use memory resources individually:

VM_A: assign 16GB, use 17%,

VM_B: assign  96GB, use 42.64%

CVM:  assign 32GB , use 79.83%

That node show it consumed 78.08% of memory, according to the above usage, if you look at the actual usage, it would not consume more than half of the node, the consumption data displayed by this node is similar to the memory setting value of the virtual machine?

Hi @Wei Cheng 

The value displayed for the host is similar to the sum of values of memory settings of the VMs that are running on that host. It is because memory overprovisioning doesn’t work on AHV and you can’t allocate more memory to your VMs than the host has.

There is no memory oversubscription in AHV in the current versions.

Is there a plan to support Memory oversubscription in the near future? 

This is the only thing holding us from switching from vSphere to AHV. Unfortunately, we can’t afford to add memory on all the boxes. 

Hi DKim,

it’s on the roadmap, but not for the near future. There is no concrete ETA at this time. Currently, planned for the 2nd half of 2021.

Hi,

Following up on this feature/functionality request. The Q2 2021 date has passed. Is this memory over-provisioning still on the roadmap? Is there an ETA for release?

Thanks, Benjamin

Hi Benjamin,

yes, it is going to be in the AOS 6.1 that is coming really soon. Expected in February or if some late issues are found during the testing, in March. 

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