prlctl utility cannot increase container diskspace above 4 Tb.
Attempts to resize the container to more than 4 Tb (
~# prlctl set 100 --diskspace 5T) will be reported as successul, however the diskspace inside the container will actually be set to 944G (1Tb minus diskspace needed for file-system structures).
The problem is recognized as product issue PSBM-25222.
vzctl tool to resize the container's disk:
~# vzctl set 100 --diskspace 5T
The issue will be fixed in one of the future product updates.