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Devator
Asked: 2012-11-12 14:15:40 +0800 CST

Bad network performance on KVM guest

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I have a dedicated server connected to a 1000 Mbit port. However, the Debian guest is only getting half to a 1/4 the speeds:

On the node itself (Linux node 2.6.32-279.9.1.el6.x86_64 #1 SMP Tue Sep 25 21:43:11 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux): 

wget http://www.bbned.nl/scripts/speedtest/download/file1000mb.bin -O /dev/null
--2012-11-11 23:10:11--  http://www.bbned.nl/scripts/speedtest/download/file1000mb.bin
Resolving www.bbned.nl... 62.177.144.181
Connecting to www.bbned.nl|62.177.144.181|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1048576000 (1000M) [application/octet-stream]
Saving to: â/dev/nullâ

100%[====================================>] 1,048,576,000  100M/s   in 10s

2012-11-11 23:10:21 (100 MB/s) - â/dev/nullâ

On the guest (Debian 6.0.5, x64: Linux debian 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64 GNU/Linux):

wget http://www.bbned.nl/scripts/speedtest/download/file1000mb.bin -O /dev/null
--2012-11-11 23:10:41--  http://www.bbned.nl/scripts/speedtest/download/file1000mb.bin
Resolving www.bbned.nl... 62.177.144.181
Connecting to www.bbned.nl|62.177.144.181|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1048576000 (1000M) [application/octet-stream]
Saving to: â/dev/nullâ

100%[=================================================================================================================================================================================================>] 1,048,576,000 16.5M/s   in 42s

2012-11-11 23:11:23 (23.8 MB/s) - â/dev/nullâ

I use the virtio NIC. I tried some more NICs: e1000 and the Realtek 8139 but those yield even worse results.

Anyone has an idea how to improve these speeds?

centos

1 Answers

  1. Best Answer

    It has been fixed with:

    service iptables stop
echo > /etc/sysconfig/iptables
service iptables start

    It seems there were some mangle iptable rules.

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