VAAI UNMAP and Performance Considerations
VMware VAAI (vSphere APIs for Array Integration) has been heavily leveraged for VMware storage environments. Using these integrated APIs, the underlying hardware can offload storage tasks from the hypervisor to get the greatest efficiency and performance
*Performance May Vary
As with many features inside a product, there are some knobs to turn sometimes in order to ensure that everything is tuned for performance and stability. The VAAI capabilities are not one of those things, but In practice, it was found that there can be some challenges with the UNMAP process which reclaims storage space. As quoted by Cormac from his article on the subject:
Prior to this capability, the ESXi host had no way of informing the storage array that the space that was being previously consumed by a particular VM or file is no longer in use.
Luckily, we have access to a team of experts who were able to shed some light on the potential issue and why performance may vary depending on the storage usage pattern.
You can view Cormac Hogan’s great post here on the subject and learn about the VAAI UNMAP Performance Considerations.