To maintain a constant connection between a host and its storage, ESXi supports multipathing. Multipathing is a technique that lets you use more than one physical path that transfers data between the host and an external storage device.
In case of a failure of any element in the SAN network, such as an adapter, switch, or cable, ESXi can switch to another physical path, which does not use the failed component. This process of path switching to avoid failed components is known as path failover.
In addition to path failover, multipathing provides load balancing. Load balancing is the process of distributing I/O loads across multiple physical paths. Load balancing reduces or removes potential bottlenecks.
Virtual machine I/O might be delayed for up to sixty seconds while path failover takes place. These delays allow the SAN to stabilize its configuration after topology changes. In general, the I/O delays might be longer on active-passive arrays and shorter on active-active arrays.