The way in which hosts are connected upstream for network and storage access can vary significantly, depending on hardware choices, legacy infrastructure, vendor constraints, cost, and protocols employed.

However, because a number of virtual machines are typically consolidated onto a single host, it is important that the bandwidth capabilities within the infrastructure not be overlooked. With smaller form factor commodity hardware, the number of I/O slots is typically limited, and those slots might have to provide storage connectivity in addition to IP network connectivity. These types of restrictions promote the use of 10-gigabit Ethernet interfaces or Converged Network Adaptors (CNAs), both of which will allow for the consolidation of multiple interfaces and data types into a single, or ideally dual, sizable bandwidth interface.

 

Regardless of the type of NIC, CNA or HBA employed, two ports of each type are typically required for redundancy. For Fibre Channel or FCoE connectivity, each interface is treated as a separate entity, with the load balancing being carried out using multipathing (MPIO) software. From an IP network interface controller (NIC) perspective, load balancing can be achieved through VMware vSphere Network I/O Control. In addition, the NICs can be configured in two different ways. In Active/Active mode, the interfaces are aggregated into a single port channel or used as separate entities. In Active/Passive mode, the passive interface waits for the active interface to fail before becoming active and transmitting and receiving data packets.

When designing and scaling host connectivity, in addition to virtual machine traffic, it is important to identify other system traffic types and their impact on the platform. IP storage, vSAN, and system-level traffic, such as heartbeats and vMotion will all affect the design.

Finally, if data is being replicated directly from the host, as is the model with VMware vSphere Replication™, verify that the design allows for sufficient bandwidth from the host’s interface, as well as from the LAN and WAN perspective, to accommodate this data.