vStorage APIs for Storage Awareness (VASA) is a set of application program interfaces (APIs) that enables vSphere vCenter to recognize the capabilities of storage arrays. Such capabilities, including RAID, native thin provisioning and deduplication, are made visible within vCenter. This visibility makes it easier for virtualization and storage administrators to make decisions about how data stores should be maintained -- for example, choosing which disk should host a particular virtual machine (VM).
VASA also provides information about storage arrays to vSphere’s Profile-Driven Storage feature, which determines whether the device a VM is stored on complies with the VM’s storage requirements. In addition, VASA provides VMware vSphere’s Storage Distributed Resource Scheduler (DRS) with information on storage arrays so that Storage DRS can work optimally with them.
VASA was released with VMware’s vSphere 5.