To maintain a constant connection between a host and its storage, ESXi supports multipathing. With multipathing, you can use more than one physical path that transfers data between the host and an external storage device.
If a failure of any element in the SAN network, such as an adapter, switch, or cable, occurs, ESXi can switch to another viable physical path. 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 60 seconds while path failover takes place. With these delays, the SAN can 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.