Why a Windows 11 VM Shows Nearly 100% Memory Usage in Proxmox VE
A Windows 11 VM in Proxmox VE was showing nearly 100% memory usage in monitoring. Inside Windows Task Manager, however, actual memory usage was only around 30–50% . At first glance, that looks like a monitoring problem. It wasn't. The issue was in the VM configuration: the PVE Ballooning Device had been disabled , which meant Proxmox VE was not receiving the guest memory statistics needed to reflect the actual Windows memory state. I encountered this while monitoring a Proxmox VE environment with OpsHome NOC. This post documents how I traced the discrepancy and fixed it. The symptom On the same Proxmox VE host, the memory usage of Ubuntu VMs looked normal. One Windows 11 VM was different. The VM had 24 GB of RAM configured, but the monitoring result remained close to: Memory: 100% Used: about 24.2 GB Total: 24 GB Inside Windows 11 Task Manager, however, the VM was clearly not using all of its memory. The difference looked roughly like this: Monitoring: 90%–100% Windows 11: 30%–50% That is too large a difference to treat as a normal sampling variation. If you encounter something similar, especially when Linux VMs on the same Proxmox host look normal, do not immediately assume: Windows has a memory leak The monitoring threshold is wrong The monitoring application is calculating memory incorrectly The more important question is: Is Proxmox VE actually receiving the correct memory statistics from the Windows guest? Checking BalloonService inside Windows 11 For Proxmox VE to obtain useful guest memory statistics from a Windows VM, the VirtIO Balloon driver and its related Windows service need to be available. Inside Windows 11, I opened PowerShell and checked BalloonService: Get-Service * balloon * The result showed: Running BalloonService So the Windows-side BalloonService was already installed and running. At this point, the guest-side service did not appear to be the problem. The next step was to check the VM configuration on the Proxmox side. Checking the Proxmox VE