When I test my own '10 Gigabit' instances (c3.8xlarge) with iperf I won't see transfer rates exceeding 1.73 Gbps. This is at least four times worse than what a blogger at scalablelogic reports where tests show results of 7 Gbps and 9.5 Gbps.
I'm testing between two c3.8xlarge instances located in the same zone and region, so these should be optimal benchmarking conditions. The one c3.8xlarge acts as iperf server and the other as an iperf client. Both instances are launched with Amazon Linux AMI 2013.09.2 - ami-5256b825 (64-bit).
Why am I seeing such poor results?
What should I look at if I want to improve throughput?