To get overview of your disk capacity run following commands in order:

gnt-disks.sh
gnt-pv-usage.sh
gnt-vg-usage.sh
gnt-lvs.sh

If this doesn't return enough information you can try smart:

refresh smart dumps in /dev/shm with:

./gnt-smart.sh clean

and generate report:

./gnt-smart-query.sh Power_On_Hours