I've set up a nice Ubuntu+KVM based DRBD cluster and everything seems to fine except for when I try to view one of the websites running inside one of my virtual machines - it's really slow... I have LXDE installed on the host and have tested viewing the VM websites there and they are extremely fast - only about 2-3 seconds for a fairly complex page (compared to about 25 seconds when I view the same site externally). Because of this, I don't think it's a problem with Apache or KVM disk I/O.
I suspect that the problem is with the new switch I put the servers behind, but I can't be 100% sure. What tools should I use to detect where a network bottleneck is? I'm toying around with iperf at the moment, but my boss is looking to me for an absolute as to what and why the connection is slow.