Still playing with KVM (Kernel-based Virtual Machine), this time checking out some networking features. I've been running Ubuntu 8.04 LTS Server (Hardy Heron), both as the host and as a VM on that host. Networking is setup to use a bridge.
KVM offers different emulated NICs, I took a quick look at running
iperf between the VM and the host, and got these speeds for a few select NIC models:
- RTL-8139C+ (the default): ~210 Mb/sec
- Intel e1000 (somewhat recommended here): ~ 330Mb/sec
- virtio: ~ 700Mb/sec
The thing about virtio though is that it doesn't work when the VMs RAM is set to 4GB. So I guess you can have fast networking, or lots of memory, but not both.