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VMware vSphere Virtual Volumes (VVols) Interoperability: VAAI offloads and VVols storage (2113789)

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Purpose

This article defines how vStorage APIs for Array Integration (VAAI) coexists with Virtual Volume (VVol) APIs (also referred to as VASA APIs).

Resolution

VMware vSphere API for Storage Awareness (VASA) is a set of APIs that permits arrays to integrate with vCenter Server for management functionality.

With vSphere 4.x, VMware introduced VMware vStorage APIs for Array Integration (VAAI), also called hardware acceleration or hardware offload APIs, which are a set of APIs to enable communication between VMware vSphere ESXi hosts and storage devices. Both Block and Network Attached Storage (NAS) VAAI APIs are supported.

Both VASA and VAAI belongs to the same family of Storage APIs, used by third-party hardware, software and storage providers to enhance several vSphere features and solutions. The two features work independently, but can coexist.

In VMware vSphere 6.0, Virtual Volumes (VVols) introduces a new set of VASA APIs. With VVols, the storage array systems are aware of a virtual machine's disk. They can efficiently perform operations such as snapshots, clones, and zeroing operations on the virtual machine's disks.

In a situation where you are migrating between (either to or from) a VVol and non-VVol storage, since the VASA offloads is not defined for the non-VVol storage, you end up relying on VAAI.

The storage migration operation goes through these setps with VVols:
  1. Attempt VASA APIs offloads first.
  2. The array does not support VASA APIs, the operation falls back to host orchestrated clone, and then attempts to use hardware (VAAI) data mover.
  3. If hardware offloads (VAAI primitives) are available, then VAAI is used.
  4. If hardware offloads (VAAI primitives) are not available (for reasons that the array does not support VAAI or the VAAI-NAS plug-in is not available), the software data mover/host based copy process is used instead.
If it is a VVol array and the VSAN API call fails or is not applicable, the VAAI APIs are used instead. If VAAI fails, the legacy data mover methods are used instead.

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