The physical network infrastructure must be capable of supporting the total throughput requirement of the environment. The total throughput requirement is calculated by multiplying the number of virtual machines by the throughput that's required by a single virtual machine:
100 Virtual Machines x 10 Mbps = 1,000 Mbps Total
The throughput that's required for a single host is calculated by multiplying the number of virtual machines that will run on a host by the throughput that's required by a single virtual machine:
20 Virtual Machines x 10 Mbps = 200 Mbps per Host
Network adapters are generally capable of delivering throughput equal to approximately 80 percent of the adapter speed, for example, 800 Mbps for a 1 Gbps network adapter. A single gigabit Ethernet connection would provide sufficient bandwidth to support the virtual machine throughput requirements that were calculated previously. An additional network adapter would be required to support failovers.
There are also network bandwidth requirements to support VMkernel interface network connectivity for management, vMotion, IP storage, and Fault Tolerance. The minimum bandwidth requirements for VMkernel network connectivity are as follows:
- Management: 100 MB
- vMotion: 1 GB
- IP storage: This is dependent on the amount of storage throughput required, but is limited to the bandwidth of a single path
- Fault Tolerance: 1 GB (10 GB required for multi-vCPU FT)
Sufficient physical network connectivity and bandwidth must be included in the design to support these services.
Network connectivity can be provided by using multiple 1 GB network adapters, or 10 GbE Converged Network Adapters (CNAs) can be used to carry multiple network traffic types, including virtual machine network traffic and VMkernel (management, vMotion, FT, and IP storage) network traffic on a single 10 GbE network adapter, as shown in the following diagram:
When CNAs are used to provide physical uplink connectivity to virtual switches, traffic shaping or Network I/O Control (NIOC) may be configured to ensure that sufficient network bandwidth is available to each traffic type serviced by the CNAs.