Ballooning Ram acting weird

[rackdie]

Whenever I allocate minimum memory to a vm the vm starts to consume all of its ram even when idle but when i check host the host is freeing up ram so ballooning works normal. But the problem is with vm, that when it consumes 98% of ram i cant carry out any work in it since apps crash due to no memory available. when i set minimum memory to the maximum memory then no ballooning works and ram on task manager and proxmox dashboard falls back to normal which is like 900mb while idle. Any way to fix this?

 

[leesteken]

That's how ballooning works. You need to set the minimum memory of the VM high enough that the VM does not get into trouble. Ballooning just takes away memory when the host memory (or memory plus swap) gets to 80%. If you want to share identical memory between VM, use KSM and configure it to start sharing memory (much) earlier (than 80%).

 

[rackdie]

for eg my vm now wants to use full 6gm ram for some work. will the memory that was freed to the host be used by the VM from the host or will i expect crashes?

 

[Dunuin]

Ballooning doesn'T care if your VM needs that RAM or not. It will just remove that RAM from the VM until either all VMs reached the defined "Min RAM" or until the Hosts RAM usage drops below 80%. So if you set Min RAM to 1GB and Max RAM to 6GB, it will slowly steal 5GB of RAM and the VM has to handle it...where the VM will usually first drop some caches and then start to kill processes, until everything fits in the 1GB of RAM that the VM got.

 

[rackdie]

So does ballooning affect VM Performance overall?