A VSA cluster leverages the computing and storage resources of several ESXi hosts and provides a set of datastores that are accessible by all hosts within the datacenter.
An ESXi host that runs a vSphere Storage Appliance and participates in a VSA cluster is a VSA cluster member. With vSphere Storage Appliance, you can create a VSA cluster with two or three VSA cluster members. The status of the VSA cluster is online only when more than half of the members are online.
A VSA cluster enables the following features:
Shared datastores for all hosts in the datacenter
Replica of each shared datastore
vSphere vMotion and vSphere HA
Hardware and software failover capabilities
Replacement of a failed VSA cluster member
Recovery of an existing VSA cluster
Depending on a licensing model you use, you can have several clusters managed by a single vCenter Server.