EnableBlockDelete is a setting in ESXi that has been around since ESXi 5.0 P3 I believe. It was initially introduced as a way to turn on and off the automatic VMFS UNMAP feature introduced in 5.0 and then eventually canned in 5.0 U1.
The description of the setting back in 5.0 was “Enable VMFS block delete”. The setting was then hidden and made defunct (it did nothing when you turned it off or on) until ESXi 6.0. The description then changed to “Enable VMFS block delete when UNMAP is issued from guest OS”. Continue reading In-Guest UNMAP, EnableBlockDelete and VMFS-6