Even when well and truly used. Updated to HS only Sunday, but is it not risky when 400GB used of 500? Can't mess things up can it
I have never seen it causing anyone any issues when enabled. It just changes how it writes data and how it moves it around going forward. Enabling it doesn’t cause any rewrite of current data in the moment.
I say all this with almost 100% confidence but you should search here. Lots of threads on it. Also, do you backup? I use CCC to clone my internal drive to a bootable FireWire drive. Peace of mind.