Connections on the vRack allows you to max out the secondary network adapters connection. The maximum bandwidth would be the lowest port speed where by if we have 2 servers and one server vRack port is 1 Gbps and the 2nd server vRack port is 10Gbps, the bandwidth between the two servers will be 1 Gbps. Naturally if both servers have 10 Gbps vRack ports then they will communicate at the maximum bandwidth.
We can look to test the vRack port via an iperf test to check the bandwidth of the vRack connections. We will have 1 server in the BHS datacenter and another in the RBX datacenter. You can see more information regarding the datacenters here.
The two datacenters are physically apart. Where by BHS is in Canada and RBX is physically in France. We will look to use the iperf command to test the bandwidth between the two servers:
firstname.lastname@example.org:~# iperf -c 192.168.0.50 -i1 -P100 | grep SUM [SUM] 0.0- 1.0 sec 118 MBytes 987 Mbits/sec [SUM] 1.0- 2.0 sec 124 MBytes 1.04 Gbits/sec [SUM] 2.0- 3.0 sec 118 MBytes 989 Mbits/sec [SUM] 3.0- 4.0 sec 113 MBytes 950 Mbits/sec [SUM] 4.0- 5.0 sec 112 MBytes 937 Mbits/sec [SUM] 5.0- 6.0 sec 114 MBytes 958 Mbits/sec [SUM] 6.0- 7.0 sec 110 MBytes 921 Mbits/sec [SUM] 7.0- 8.0 sec 114 MBytes 960 Mbits/sec [SUM] 8.0- 9.0 sec 112 MBytes 937 Mbits/sec [SUM] 0.0-10.4 sec 1.13 GBytes 934 Mbits/sec
As we can see the physical port is 1 Gbps and at one point we are able to achieve the full network capacity however due to network overheads, we can get approximately 934 Mbps to 1 Gbps throughput.