In the ext file system (ext2/ext3/ext4), the area that can be used only by the root user is reserved, so the disk space may not be fully used. By default, 5% of the partition size is secured, but with a 2TB hard disk it will be 100GB, so you will not be able to use the size that can not be ignored.
shell
# tune2fs -m 0 ${device}
-m option0% is fine as long as it is a partition dedicated to user data that does not contain system files. There is no point in allocating a dedicated area for root unless it is a system area because it is intended to prevent the operation of the system from being affected even if some users use the data to the full.
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