The webui for ESXi seems to interpret the command to cancel a task more as a polite request rather than a command. I have yet to hit the cancellation button and the task actually cancels and it isn't for things that shouldn't be immediately canceled. For example, I started moving a large file between two drives. The VM is unregistered and powered off. I started moving it and realized I'd rather just delete it so I hit cancel task.... annnnnnd it just keeps trekking on moving those files like I did nothing.

Moving files is not something that needs additional compute before coming to a halt. Just stop doing it - immediately. It has gone 6% more on a several hundred gig transfer and shows no signs of stopping.

Question: How do you cancel a task via the webui? The cancel task button doesn't actually seem to do anything.

Update: I hit cancel task when it was at 6% (and have clicked it several times more subsequently). It is now at 25% - the task still hasn't canceled.