These rules are based on data services that storage entities such as Virtual SAN and Virtual Volumes advertise.
To supply information about underlying storage to vCenter Server, Virtual SAN and Virtual Volumes use storage providers, also called VASA providers. Storage information and datastore characteristics appear in the VM Storage Policies interface of the vSphere Web Client as data services offered by the specific datastore type.
A single datastore can offer multiple services. The data services are grouped in a datastore profile that outlines the quality of service that the datastore can deliver.
When you create rules for a VM storage policy, you reference data services that a specific datastore advertises. To the virtual machine that uses this policy, the datastore guarantees that it can satisfy the storage requirements of the virtual machine. The datastore also can provide the virtual machine with a specific set of characteristics for capacity, performance, availability, redundancy, and so on.
For more information about storage providers, see Using Storage Providers.