Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

My setup:

  • Proxmox on the host machine with vmbr0 bridge for guests and a shorewall firewall
  • Guests (both KVM not openvz):
    • Windows Server '08
    • Debian lenny

I can download a speed test file on the proxmox host (wget) and on the windows server (firefox) with about 8-10MB/s. But when I download the file with wget on the debian guest it's only 2-3MB/s. Both guests use the same network bridge, both have 'rtl8139' as the network card in KVM.

Someone knows how to fix that? I want to use the debian VM as a webserver so it needs some bandwidth.

share|improve this question
up vote 0 down vote accepted

If you use kvm you should:

  • disable the io scheduler with bootstring elevator=none
  • use virtio net drivers
share|improve this answer

agreed on the virtio drivers. the scheduler I prefer for hosts is deadline though

Besides that, have you checked with tcpdump what is going on underneath the hood?

share|improve this answer
deadline is a good guess for the kvm server - but it does not make sense to have a scheduler in the server and in all guests... – Andreas Rehm Sep 10 '10 at 11:58
yeah, the guests don't need it. I haven't seen cfq get in the way though, and I have lots of guests on KVM – dyasny Sep 10 '10 at 12:09

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.