disable RAM overprovisioning

[IamPepsiGuy]

Is it possible to disable RAM overprovisioning? I'm new to Proxmox. I created and started more VMs that I have physical RAM. I'm familiar with ballooning and the VMs have the ballooning driver installed in the guest, but the startup of the VMs happened too quickly so a VM that was running for a while ended up getting killed by OOM.

I would like to just never overprovision RAM -- but I'd like Proxmox to just fail to start a new VM if there is insufficient RAM to do so (e.g., having Proxmox calculate the max memory of all running VMs plus whatever overhead that Proxmox itself needs, and if there is less remaining then needed by the VM that is requested to start, inform the user that there is insufficient resources to start the VM).

Is this possible? To ensure that OOM never kills a running VM.

 

[datschlatscher]

Proxmox does not include such a feature as of yet.

(e.g., having Proxmox calculate the max memory of all running VMs plus whatever overhead that Proxmox itself needs, and if there is less remaining then needed by the VM that is requested to start, inform the user that there is insufficient resources to start the VM).

This is a little complicated due to features like memory ballooning. When Proxmox starts a VM, it does not have a sure way of telling how much RAM a VM is going to need. It will simply give the VM more memory as requested, as long as it is under the configured limit.

I'm afraid, for now, you will have to simply configure your VMs in such a way that they do not exceed your systems total memory to not invoke the OOM.

 

[IamPepsiGuy]

Just to make sure I'm not missing something, anytime I start a VM on a node (or before I migrate a VM to a node), I need to manually add up all the max memory of all running VMs on target node before I attempt operation?

I was hoping there was a way to turn off RAM overcommitting and ballooning and just allow the system to handling the math to prevent any OOM issues. I don't want my poor math to result in a kill to a critical VM.

 

[datschlatscher]

I was hoping there was a way to turn off RAM overcommitting and ballooning and just allow the system to handling the math to prevent any OOM issues. I don't want my poor math to result in a kill to a critical VM.

Well, if you don't want to rely on your own math skills you can, of course, write a script to help you with that.
Doing this in a universal way to include most use-cases is just not so trivial, though.
From what I can tell, this does not seem like a feature a lot of people request right now, however, if you want, you can open a feature request on our Bugtracker for this, where you and potentially also other users can further outline your use-case: https://bugzilla.proxmox.com/

I need to manually add up all the max memory of all running VMs on target node before I attempt operation?

Nonetheless, if you absolutely want to make sure your VMs do not get killed because of overcommitted RAM, you will have to do something like that.