MechWright - 2020-12-08

Hi all,
I have the following problem:

I created a 5,5 Terabyte Veracrypt container on a 6 Terabyte external SSD drive. When I mount it, it shows the size correctly, but only allows me to access 4,7 TB (we couldn't fully back up a 5,3 TB server). Also going to
/media/veracrypt1 and running df -h on a similarly prepared but almost empty eSDD gives
Filesystem Size Used Avail Use%
/dev/mapper/veracrypt1 5,0T 89M 4,7T 1%
Why am I deprived of 800 GB on a 5,5 TB drive?