VMware has released a whitepaper that details some technical information about the VSA. In the release of VMware vSphere 5.0, VMware also released a new software storage appliance called the VMware vSphere Storage Appliance (VSA). VMware VSA provides an alternative shared storage solution to Small to Medium Business (SMB) customers who might not be in a position to purchase a Storage Area Network (SAN) or Network-Attached Storage (NAS) array for their virtual infrastructure. Without shared storage configured in a vSphere environment, customers have not been able to exploit the unique features available in vSphere 5.0, such as vSphere High Availability (HA), vSphere, vMotion and vSphere Distributed Resource Scheduler (DRS). The VSA is designed to provide “Shared Storage for Everyone”.
See the whitepaper here.