High Bandwidth (Download) Causes VM to Lockup


New Member
Jun 25, 2021
Hi there,

I'm having an issue on my hosts (2) wherein whenever I download large files/ISO's or run Speedtests etc and it consumes most of the available bandwidth for my ISP downlink (1Gbps), it seems to tank the Windows VM I am using at the time to download. I am connecting to the Windows VM's over RDP - using the console/VNC seems to be fine

I used the VirtIO drivers from Red Hat to get the NIC working and on both of the VM's. On both hosts I am using the Realtek RTL8139 NIC drivers. When creating the VM, I made no changes to the alternate configs, such as the CPU flags:


The disks are QEMU image format (qcow) and there is 'No cache' (I believe I should have set this to writeback(?)?

Specs of the hosts are OVH GAME-2 servers:

16 x AMD Ryzen 7 5800X 8-Core Processor (1 Socket)
Kernel Version

Linux 5.13.19-6-pve #1 SMP PVE 5.13.19-14 (Thu, 10 Mar 2022 16:24:52 +0100)
PVE Manager Version


1TB SSD x 2 in RAID 1

Load on the server is around 10-20% on average and the VM's are suffiently spec'ed

I am using pfSense to sort the networking on both hosts, resource usage on pfSense when downloading said large files is good

Everything else is running smoothly




Version dump:

pve-manager/7.1-10/6ddebafe (running kernel: 5.13.19-6-pve)
root@lon-dc01:~# pveversion 0f
USAGE: pveversion [--verbose]
root@lon-dc01:~# pveversion -v
proxmox-ve: 7.1-1 (running kernel: 5.13.19-6-pve)
pve-manager: 7.1-10 (running version: 7.1-10/6ddebafe)
pve-kernel-helper: 7.1-12
pve-kernel-5.13: 7.1-9
pve-kernel-5.4: 6.4-10
pve-kernel-5.13.19-6-pve: 5.13.19-14
pve-kernel-5.13.19-5-pve: 5.13.19-13
pve-kernel-5.13.19-3-pve: 5.13.19-7
pve-kernel-5.13.19-2-pve: 5.13.19-4
pve-kernel-5.4.151-1-pve: 5.4.151-1
ceph-fuse: 14.2.21-1
corosync: 3.1.5-pve2
criu: 3.15-1+pve-1
glusterfs-client: 9.2-1
ifupdown: 0.8.36+pve1
libjs-extjs: 7.0.0-1
libknet1: 1.22-pve2
libproxmox-acme-perl: 1.4.1
libproxmox-backup-qemu0: 1.2.0-1
libpve-access-control: 7.1-6
libpve-apiclient-perl: 3.2-1
libpve-common-perl: 7.1-3
libpve-guest-common-perl: 4.1-1
libpve-http-server-perl: 4.1-1
libpve-storage-perl: 7.1-1
libspice-server1: 0.14.3-2.1
lvm2: 2.03.11-2.1
lxc-pve: 4.0.11-1
lxcfs: 4.0.11-pve1
novnc-pve: 1.3.0-2
proxmox-backup-client: 2.1.5-1
proxmox-backup-file-restore: 2.1.5-1
proxmox-mini-journalreader: 1.3-1
proxmox-widget-toolkit: 3.4-7
pve-cluster: 7.1-3
pve-container: 4.1-4
pve-docs: 7.1-2
pve-edk2-firmware: 3.20210831-2
pve-firewall: 4.2-5
pve-firmware: 3.3-5
pve-ha-manager: 3.3-3
pve-i18n: 2.6-2
pve-qemu-kvm: 6.1.1-2
pve-xtermjs: 4.16.0-1
pve-zsync: 2.2.2
qemu-server: 7.1-4
smartmontools: 7.2-pve2
spiceterm: 3.2-2
swtpm: 0.7.1~bpo11+1
vncterm: 1.7-1
zfsutils-linux: 2.1.2-pve1


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