Score:1

kvm / proxmox 5 - virtio_net slow network 5Mbit, sometimes 900Mbit in opposite or both direction

cn flag

Environment:

  • several PROXMOX 5 (KVM) servers (kernel: 4.15.18-30-pve)
  • VMs running Debian 9, 10 and 11 (vitrio /qemu-guest-agent current version of the respective Debian version)
  • network cards connected via virtio_net kernel module
  • VMs connected via Linux bridge
  • 1Gbit network switches

Problem

  • VMs mostly transfer with only about 5 Mbit/s
  • sometimes the full transfer rate of about 950Mbit/s is reached, when tested in the opposite direction it is often (not always) only 5 Mbit/s
  • transfer rates between VMs on one host are ok about 20Gbit/s (old servers)

Tests

  • tests were done via iperf3
  • the transfer rate between KVM hosts is ok, about 950Mbit/s in both directions
  • I moved the VMs back and forth between the hosts without seeing a pattern to the problem.
  • The tests were done with different VMs (Debian 9-11)

Test both directions vm to vm (perf3)

root@@HOST1:~# iperf3 -c @HOST2
Connecting to host @HOST2, port 5201
[  5] local 192.168.40.121 port 59440 connected to 192.168.40.52 port 5201
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   109 MBytes   918 Mbits/sec   22    352 KBytes
[  5]   1.00-2.00   sec   107 MBytes   900 Mbits/sec   16    253 KBytes
[  5]   2.00-3.00   sec   107 MBytes   898 Mbits/sec    2    390 KBytes
[  5]   3.00-4.00   sec   108 MBytes   910 Mbits/sec    7    423 KBytes
[  5]   4.00-5.00   sec   109 MBytes   913 Mbits/sec    3    419 KBytes
[  5]   5.00-6.00   sec  93.3 MBytes   783 Mbits/sec   19    165 KBytes
[  5]   6.00-7.00   sec  92.3 MBytes   775 Mbits/sec    3    375 KBytes
[  5]   7.00-8.00   sec   107 MBytes   895 Mbits/sec   27    358 KBytes
[  5]   8.00-9.00   sec   110 MBytes   920 Mbits/sec    9    322 KBytes
[  5]   9.00-10.00  sec   109 MBytes   914 Mbits/sec   17    327 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  1.03 GBytes   883 Mbits/sec  125             sender
[  5]   0.00-10.04  sec  1.02 GBytes   876 Mbits/sec                  receiver

iperf Done.
root@@HOST1:~# iperf3 -s
---------------------------------------------
Server listening on 5201
---------------------------------------------
Accepted connection from 192.168.40.52, port 35006
[  5] local 192.168.40.121 port 5201 connected to 192.168.40.52 port 35008
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec   598 KBytes  4.90 Mbits/sec
[  5]   1.00-2.00   sec   699 KBytes  5.72 Mbits/sec
[  5]   2.00-3.00   sec  1.38 MBytes  11.6 Mbits/sec
[  5]   3.00-4.00   sec   871 KBytes  7.14 Mbits/sec
[  5]   4.00-5.00   sec  1.36 MBytes  11.4 Mbits/sec
[  5]   5.00-6.00   sec  1.43 MBytes  12.0 Mbits/sec
[  5]   6.00-7.00   sec  1.23 MBytes  10.3 Mbits/sec
[  5]   7.00-8.00   sec   592 KBytes  4.85 Mbits/sec
[  5]   8.00-9.00   sec  1.20 MBytes  10.1 Mbits/sec
[  5]   9.00-10.00  sec  1.35 MBytes  11.4 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-10.04  sec  10.6 MBytes  8.89 Mbits/sec                  receiver
---------------------------------------------
Server listening on 5201
---------------------------------------------

Configuration NIC

  • server side 1Gbit/s full duplex (tested with ethtool)
  • Intel adapter

Does anyone have any ideas how I can further isolate the problem or even know the problem.

djdomi avatar
za flag
at first, proxmox 5 is eol... since ages! Consider an upgrade. Second i would suggest since you use it in an business environment, you bought the support usually and know that you can use the support of the proxmox vendor?! proxmox.com is the vendor and i think that the question would better fit there
dominix avatar
gf flag
how accurate is your virtio_net driver ? which iso of virtio ? which version ?
farax avatar
cn flag
Thank you very much for the advice. Unfortunately, it is not at my discretion to decide whether to purchase the support or upgrades. I have added information about the versions.
djdomi avatar
za flag
however, the forum is also open for public and community, and may be more specific instead a general w&a site
mangohost

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