This document has not been formally reviewed for accuracy and is provided "as is" for your convenience.
Differences between DF and DU Linux commands are not always clear, especially when working with SMAX.
Not enough knowledge on Linux OS and how the disk volumes works.
DU command gets usage size based on file total size in the disk and DF gets the size at OS level, so for example:
Some file may be already deleted in the disk, but some process still collects its volume information, hence the output difference.
In order to fix that a disk de-fragmentation is needed.
Both commands should match after this.
Rebooting the system may or may not solve the issue, so it is safer to run the disk defragmentation.
Tested on SMAX 2019.11.