Slow network and high CPU usage on VMs sharing same bridge

[aluputi]

I'm having an issue and I can't figure out what's wrong. When I'm copying files between VMs sharing same network bridge I only get 30-40MBps and the host and VM CPU usage rises. The VMs are all running updated CentOS 7 with virtio for disk and network. I get the same speeds using different protocols (rsync, scp, samba).

Copying a file in the same VM from one location to another gives me at least twice the speed, so it's not disk related. Also, copying the file to some other network location fills the GB network connection. Even copying a file between VMs running on different disk drives only reach the mentioned speeds when sharing the same bridge.

I tried this on three different servers from different locations and all of them running on enterprise hardware.
I think this can be easily replicated by anyone.

Did anyone else notice this issue? What could be the fix?

Thanks!

 

[wolfgang]

Hi,

what vNIC type do you use?

Please use the only virtio.
with virtio you should have near the speed of your physical NIC.

 

[aluputi]

I only use virtio, as I mentioned in the first post. Apparently the issue was related to the firewall running in the VMs.

What's still curious is that this only happens when transferring data between VMs running on the same server and not cross-server, even though they all have the same firewall installed.