[SOLVED] Super VM very Slow


Jan 19, 2021
Hi, I'm new on proxmox world, and like it, i'm plannig a full migrate from Windows Hyper-V to Proxmox VE

I have a testing server (HP Proliant dl360 gen10 32 cores, 128gb ram, raid 1 hpe ssd 240gb mu)

with a windows guest (windows server 2016, 12cores host type, 64gb ram, 60gb qcow2, virtio drivers already installed, machine type q35 with sata controller).

This vm is a windows terminal server for a administrative app my problem is: the application runs very slow and everything inside windows run slow too, windows search, windows start menu disappear at heavy loads, office runs slow too.

i have a vm create on hyper-v with same specs(cpu,ram,disk) on exact physical server on production side, and everything runs perfect. so this isn't a software fail in the application code.

i don't know if my proxmox installation need some tuning (is very standard for now) for the size of the vm hardware.

can anybody help me please?

Thanks in advance
using qcow2 for guest disks might reduce performance. You should consider using RAW-device on LVM or ZFS.
Also adding many cores to a Windows-Guest if not "really" needed forces the hypervisor to unusual high context switching.

Start with 2 cores or 4 and check how it runs.
also, could you post the vm config ? ('qm config ID' on the cli)
Yeah sure!, thanks for the help

agent: 1
balloon: 2048
boot: order=sata1
cores: 12
machine: q35
memory: 65536
name: P-ERIS-TS2016
net0: virtio=00:15:5d:E9:F2:39,bridge=vmbr2
numa: 0
onboot: 1
ostype: l26
sata1: VMDISK:935/vm-935-disk-0.qcow2,size=90G,ssd=1
scsihw: virtio-scsi-pci
smbios1: uuid=e099c673-8b25-411d-9a2a-911c81f1516d
sockets: 2
startup: order=3
vga: qxl
vmgenid: 705f0742-fe26-4c5c-b2b2-edc49f379612
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check if memory ballooning is disabled.
Also you should change from SATA to VirtIOBlock or SCSI.
If your host has more than one NUMA-Domain enable that in your guest too.

Guest Tools and Drivers are installed?
Please disable Ballooning. It is known to sometimes cause slowdown for Windows Guests.
You wrote 12 cores in the first post, but the VM configuration has 2 sockets, which makes it 24 cores. Is this intentional? How many sockets does the host machine have?
You are using the virtual drive via SATA emulation. Switching to SCSI will increase performance and support trim/discard. This needs a VirtIO SCSI controller, which is already enabled in your configuration but is the Windows driver installed?. Maybe this also requires a block-based storage instead of the file-based qcow2, I'm not sure?
Windows does continuous disk I/O, maybe enable writeback cache for the virtual drive will help with this.
in addition to what the others said, try setting the ostype to a windows variant if the guest runs windows, there are some enhancements enabled in that case (which are not enabled when you choose 'linux' for ostype)
Hi! good morning, thanks for your time and advice
these are my current VM settings. I made the changes, so it is working better now, like a good VM :)

agent: 1
balloon: 0
cores: 10
cpu: host
machine: q35
memory: 20480
name: P-ERIS-TS2016
net0: virtio=00:15:5d:E9:F2:39,bridge=vmbr2
numa: 1
onboot: 1
ostype: win10
scsi1: VMDISK:935/vm-935-disk-0.qcow2,cache=writeback,discard=on,size=90G,ssd=1
scsihw: virtio-scsi-pci
smbios1: uuid=e099c673-8b25-411d-9a2a-911c81f1516d
sockets: 1
startup: order=3
vga: qxl
vmgenid: 705f0742-fe26-4c5c-b2b2-edc49f379612

I have a doubt, why prefer .raw instead .qcow2?


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