Architecting VMware vSAN 6.2 : vSAN Introduction : 2.3 vSAN Internal Architecture : 2.3.7 Storage Policy-Based Management (SPBM)
   
2.3.7 Storage Policy-Based Management (SPBM)
As outlined previously, SPBM is a core component of the VMware software-defined storage model and allows user control of storage policies on a per-object basis in vSAN. The Storage Policy-Based Management framework:
Exists at the vCenter Server level through the VMware vSphere Storage Profile.
Is enabled through VMware vSphere API for Storage Awareness™. (There is a vSphere API for Storage Awareness provider on each ESXi host.)
Sends the defined storage policies (if selected) to CLOMD during provisioning.
In the event that new policy is applied to a VM/disk, or if the policy is modified, those changes are reflected in SPBM and forwarded to CLOMD.
Reflects in the vSphere Web Client object status (distribution, reconfiguration/resync, and so on).