VASA is a feature that you do not need for basic VSM functionality.  Which is what the release notes are trying to say.   VASA allows VMware to query more information about storage volumes.   I.e. via VASA calls VCS can show that a volume is RAIDed storage, has snapshot or replicas.   At this time the usefulness of VASA is limited even when available.   VASA is the first step from VMware to better understand a storage arrays capabilities. More functionality will coming in future ESXi versions.  However, to make VASA work at all, the storage vendor has to provide "glue" software to perform the specific HW calls from a VCS query.   VSM is what has the code, known as a "VASA Provider".   A translator of sorts.     Regards, 
Hi. I read the release notes of Virtual Storage Manager 4.0,  vSphere License requirements these are required:  vSphere License RequirementsVSM comes with the following features and applicable licenses:VSM: Any vSphere licenseVASA: vCenter 5.0 or later, ESXi 4.0 or later, any vSphere licenseIn addition, the storage array firmware makes use of the following features regardless of whether VSM is installed:vStorage APIs for Array Integration (VAAI): Enterprise, Enterprise Plus license on ESXi4.1 or later.   Questions: 1. Will I be able to run VSM with vSphere Essentials Plus ? VAAI requires atleast vSphere Enterprise License. What are the implications if I deploy with vSphere Essentials Plus.  2. Does VSM support ESXi 5.5 U2 ?  Thanks, Paul
Dell EqualLogic HIT/VSM - VMware License Requirements.