When you define storage requirements for virtual machines and virtual disks, you reference vendor specific or user-defined storage capabilities in a storage policy.
Vendor Specific Storage Capabilities
Storage systems that use vStorage APIs for Storage Awareness, also called VASA, are represented by storage providers. Storage providers inform vCenter Server about specific storage devices, and present characteristics of the devices and datastores deployed on the devices as storage capabilities. Such storage capabilities are system-defined and vendor specific.
A storage system can advertise multiple capabilities. The capabilities are grouped into one or more capability profile. Capabilities outline the quality of service that the storage system can deliver. They guarantee that the storage system can provide a specific set of characteristics for capacity, performance, availability, redundancy, and so on.
Vendor specific capabilities appear in the Storage Policy-Based Management system. When you create a storage policy for your virtual machine, you reference these vendor specific storage capabilities, so that your virtual machine is placed on the datastore with these capabilities.
For more information about storage providers, see Using Storage Providers.
Tag-Based Storage Capabilities
You can use tags to create user-defined storage capabilities and apply those tags to datastores. You can apply more than one tag to a datastore.
Typically, tag-based capabilities serve the following purposes:
Encode policy-relevant information that is not advertised through vStorage APIs for Storage Awareness, such as geographical location or administrative group.
Attach a broad storage level definition to a datastore that is not represented by any storage provider.
All tags applied to datastores appear in the Storage Policy-Based Management system. As with vendor specific capabilities, you can use the tags when you create storage policies.