Hi everyone,
we are currently facing significant performance issues with Windows guests on both Proxmox VE 8 and 9.
Environment:
- Proxmox VE 8 and 9 (tested on multiple nodes)
- Storage:
- Local SSD (Software RAID 1)
- Ceph cluster
- Guest OS:
- Windows Server 2022
Configuration:
The VM was set up according to the official recommendations:
- VirtIO SCSI controller
- VirtIO drivers installed (latest stable ISO)
- Balloon driver installed
- QEMU Guest Agent installed and running
Problem:
The I/O performance inside the Windows VM initially appears normal, but under load it drops dramatically after a short time.
Symptoms:
- Disk throughput collapses after a few seconds of sustained load
- High latency inside the guest
- System becomes sluggish/unresponsive
- Issue occurs on both local storage (SSD RAID1) and Ceph
What we already tested:
- Different storage backends (local vs. Ceph)
- Reinstalled VirtIO drivers
- Tested with and without Ballooning
- Different disk cache modes (writeback, writethrough, none)
- Different bus types (VirtIO SCSI vs. SATA for comparison)
Observations:
- The issue seems independent of the storage backend
- Linux guests on the same hosts perform normally
- Problem appears specific to Windows guests
Questions:
- Is this a known issue with Proxmox 8/9 and Windows Guests?
- Are there recommended settings for stable I/O performance under load?
- Could this be related to VirtIO drivers or specific kernel/QEMU versions?
Any hints or similar experiences would be appreciated.
Thanks in advance.