I must be thick (pun intended), but I cant work this one out. I have an esxi5.5 with datastores on local raid controller. Please take a look at the attached screenshot.
The thin provisioned disk size is 6.6TB on datastore0 for "Hard disk 3", while physical capacity is reported correctly (5.45TB). It's not possible to decrease the provisioned size of the virtual disk. The guest OS shows disk "Hard disk 3" as 6.84TB but only containing one 3.19TB partition and the remaining space is unallocated.
No snapshots exists. Why would thin provisioned size be overbooked when no more than the currently used 1.96TB has ever been used on this datastore? Can it be undone?
Someone created disk 3 with a size of 6.5 TB. That is allowed when you use thin provisioned vmdks.
I would suggest to create a new disk just large enough to contain the data and then copy over the data.
When that is done remove the 6 tb disk and delete it.