VAAI

VAAI, or vStorage APIs for Array Integration, is a set of VMware vSphere APIs that offload specific storage operations from the ESXi hosts to the storage array. Instead of the ESXi host performing these tasks, the storage array handles them, leading to improved performance and reduced CPU overhead on the hosts. This offloading is particularly beneficial for operations such as full data copies, block zeroing, and the detection of hardware XOR capabilities. By enabling the storage array to perform these functions directly, VAAI allows hosts to focus on running virtual machines rather than managing storage tasks.

The primary VAAI primitives include Full Copy, which allows the storage array to perform a data copy operation for tasks like cloning virtual machines or creating snapshots. Atomic Test & Set is another primitive that ensures data integrity during cloning. Zeroing is used for efficient pre-allocation of disk space by instructing the array to zero out blocks. Hardware Assisted Locking helps prevent data corruption in shared storage environments. Finally, Thin Provisioning support allows VAAI to communicate with arrays that support thin provisioning, enabling better storage utilization. The adoption of VAAI can significantly enhance the efficiency and scalability of virtualized environments by leveraging the capabilities of the underlying storage hardware.