Ok now I got your doubt. Actually you are getting confused because you are seeing fixed space as formatted capacity inside VM or from Guest OS perspective. These are called thick disks, they behave similar to thinly provisioned disks. Disk blocks are only used on the back-end (array) when they get written to inside in the VM/Guest OS. Again, the Guest OS inside this VM thinks it has this maximum size from the start. There are two types of Thick disks in ESX apart from Thin disks and they are "Eager Zeroed Thick" and " Lazy Zeroed Thick". I would suggest to go through these concepts in VMWare - that will help you to understand more on this.
Hope this helps!
Regards
Subhajit
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