A device's vStorage API for Array Integration (VAAI) support status command line output shows: naa.500253825002a865 VAAI Plugin Name: ATS Status: unsupported Clone Status: unsupported Zero Status…

The vSphere Web Client derives a single VAAI status from all four primitives (ATS, Clone, Zero, Delete) and displays 'Unknown' when the results are inconsistent - in this case Zero is supported but ATS, Clone, and Delete are unsupported, which is an indeterminate state the UI cannot classify as fully supported or fully unsupported.

'Supported' would only appear in the vSphere Web Client if all relevant VAAI primitives reported a supported status, which is not the case here since three of the four are unsupported.

'Not supported' maps to all VAAI primitives returning unsupported, but because Zero Status is supported here, the device does not qualify for this classification.

'Unsupported' is not a valid display value in the vSphere Web Client VAAI status column - the UI uses 'Supported', 'Not supported', and 'Unknown' as its three possible states.