As of CDM 6.20, disk usage QoS unit is fixed to use MB (or %).
Many customers want to use GB/TB/PB as unit, because modern disk size usually starts from GB even TB.
Disadvantage by only providing MB as unit:
1. Administrator may easily make mistake when doing threshold configuration.
2. User-non-friendly in display. When operator read a disk usage is "1234567MB", he/she need to convert it to "1234GB" or "1.23TB" in his/her mind.