SSD or SAN

Convert duplicated system data, metadata and data to single copy only:

btrfs device usage /
 
btrfs balance start -sconvert=single -mconvert=single -dconvert=single / -f
# OR if data is already in single mode
btrfs balance start -sconvert=single -mconvert=single / -f
 
btrfs device usage /

Convert metadata and system data to 2 copies even if on SSD/NVM/SAN:

btrfs balance start -v -mconvert=dup,soft -sconvert=dup,soft / -f

 soft
           Takes no parameters. Only has meaning when converting between
           profiles. When doing convert from one profile to another and
           soft mode is on, chunks that already have the target profile
           are left untouched. This is useful e.g. when half of the
           filesystem was converted earlier but got cancelled.