I have software RAID6 on 8x3TB disks (18TB), there is filesystem od device /dev/md1, but EXT4 can`t be bigger than 16TB so there is 2TB of free space. I would like to use this space. My first idea was to move filesystem a little bit from the beggining of disk and than make a partition table and proper partition describing my data. But maybe there is some smart hack to retrive those 2TB, and make it easy to add another disks to this array.
Copying this data, making partitions and restoring data is not a solution.