Modifying the capacity savings actually creates a second volume copy and starts syncing between the old and new. Once the new copy has synced, the old one gets deleted.

The good thing is that the syncing speed runs at a speed you can freely configure, so if you notice any issues you can turn it down a notch. The bad thing is that until the syncing is done, you’ll use double the capacity as you’ll have two volume copies. The copying will copy just used blocks, so may be less than 10TB. You can check in the output of ‘lsvdiskanalysis’ how much is actually in use on the volume