Aggregate Allocated Used Avail Total space 5688GB 4955GB 1087GB Snap reserve 0GB 209GB 0GB WAFL reserve 753GB 77GB 675GB
So the free space percentage that you see is directly correlated to the actual physical free space.
If you'd add more disks to the aggregate or reduce the actual logical volume size to a value less than the aggregate space, then the free space percentage will be accurate.
But with thin provisioning the actual free space of the volume is not of much interest. The volume in this case is just a management entity. Deduplications and SnapShots happen on the volume basis, so that's ehy you have that in the first place.
Instead it's more important to monitor the aggregate free space. And the aggregate capacity and free space calculations are accurate, which you can see from the aggr show_space -g command above.
You basically use:
vol0: 718GB (although only 5GB used, but that volume is and should be thick provisioned, meaning "garantee=volume")
LUN Occupied Size: 5.3t (so you have written at least 5.3TB to that LUN - at least once)
A-SIS savings : 2GB (deduplication saved you 2GB)
Snap reserve: 209GB (your SnapShots occupy this amount of space)
WAFL reserve: 753GB (that's a fixed 10% reserve)
So from the 6778GB of usable capacity in your aggrgeate you use 4955GB and have 1087GB free space left
you can reduce the size of the volume until you hit the actually used capacity without losinf any data.
You should only make sure that the volume has at least the size of the LUN you provisioned, which is 6.6TB, so -500GB is safe.
The free-space percentage of the volume will change but the actual free-space will not.
As said earlier, you should not be concerned about the actual usage of the volume as you use thin provisoining. The only entity of interest is the aggregate. Once you run out of space there, your LUNs will go offline.
You could use our managebility software called "OnCommand Unified Manager" in order to help you monitor and alert on the actual free-space situation, growth rates, over-provisioning rates and so on to handle the risk of over-provisioning and make most use of your actual storage.
Thin provoisioning may become dangerous in case you don't have a proper monitoring and alerting for the actual free space in place as well as a process of remediating any space issues (either by adding disks or deleting data). It would be the same as having a smoke detector without a fire extenguisher.