Storage APIs is a family of APIs used by third-party hardware, software, and storage providers to develop components that enhance several vSphere features and solutions.
This Storage publication describes a number of Storage APIs that contribute to your storage environment. For information about other APIs from this family, including vSphere APIs - Data Protection, see the VMware Web site.
vSphere APIs for Storage Awareness
Also known as VASA, these APIs, either supplied by third-party vendors or offered by VMware, enable communication between vCenter Server and underlying storage. Through VASA, storage entities can inform vCenter Server about their configurations, capabilities, and storage health and events. In return, in certain environments, VASA can deliver VM storage requirements from vCenter Server to a storage entity and ensure that the storage layer meets the requirements.
VASA become essential when you work with Virtual Volumes, Virtual SAN, vSphere APIs for I/O Filtering (VAIO), and storage VM policies. See Using Storage Providers.
vSphere APIs for Array Integration
These APIs, also known as VAAI, include the following components:
Hardware Acceleration APIs. Allow arrays to integrate with vSphere to transparently offload certain storage operations to the array. This integration significantly reduces CPU overhead on the host. See Storage Hardware Acceleration.
Array Thin Provisioning APIs. Help to monitor space use on thin-provisioned storage arrays to prevent out-of-space conditions, and to perform space reclamation. See ESXi and Array Thin Provisioning.
vSphere APIs for Multipathing
Known as the Pluggable Storage Architecture (PSA), these APIs allow storage partners to create and deliver multipathing and load‐balancing plug-ins that are optimized for each array. Plug-ins communicate with storage arrays and determine the best path selection strategy to increase I/O performance and reliability from the ESXi host to the storage array. For more information, see Managing Multiple Paths.