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For months I've been running a few websites on a VPS and now a Wordpress website is killing my network interface.

I've just installed Wordpress and when I update the new website via wp-admin the network connection on the VPS suddenly stops working. The network interface is still up but hosts are unreachable, either via hostname or IP.

The only way to get connectivity is to take the network down and up again:

ifdown eth0; ifup eth0
  • This only happens when saving data in wp-admin
  • Posting comments via the frontend works
  • Other PHP and non PHP websites work
  • Other network applications like apt-get, ping, etc work

Nothing mentionable is reported in dmesg, syslog or /var/log/[messages|nginx]. The output of ifconfig and route seem normal.

The server install is pretty vanilla:

  • Hardware: KVM node
  • OS: Debian Lenny
  • Nginx: 0.6.32
  • PHP: 5.2.6-1 via FastCGI
  • Wordpress: 3.1.2
  • MySQL: 5.0.51a
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when you say "kill" is your interface actually down, i.e. ifconfig shows nothing for eth0? – gravyface May 18 '11 at 13:34
The interface is up, ifconfig shows the same information as before. – namsral May 18 '11 at 13:36
Are you able to ping/connect to ssh when it happens? – Bart De Vos May 18 '11 at 14:02
@Tizon No, not to or from the box. Only the lo interface is pingable. – namsral May 18 '11 at 14:33

Swapping the virtual NIC from a rtl8139 to a virtio resolved the issue. Although I still find it odd a web application can cause hickups on a network interface.

This is an answer to my own question.

share|improve this answer
rtl is an emulated device, while virtio is PV. of course it performs much much better – dyasny May 19 '11 at 7:23

Are your WordPress sites busy?

I suggest installing 'WP Super Cache' on a busy site.

WordPress doesn't have efficient sql queries and this plugin will definitely speed load times up.

It works by creating static HTML documents out of your posts instead of dynamically creating them and querying. Once installed and enabled the plugin just works. It creates new 'cached' html documents whenever the content changes (new posts, comments).

Before enabling this plugin, my server was nearly DOS'd by traffic alone!

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Thanks for the suggestion but this is a network problem not a load problem. – namsral May 18 '11 at 14:34

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