Put another way, a ton of gravel will occupy far less space than a ton of Styrofoam.   Crushed stone, for example, has a density of 100 pounds per cubic foot (lb/ft3), which is 1600 kilograms per cubic meter (kg/m3), which is 1.6 metric tons per cubic meter.
HPSS is software that manages petabytes of data on disk and robotic tape libraries. HPSS provides highly flexible and scalable hierarchical storage management that keeps recently used data on disk and less recently used data on tape.
The challenge at the DoD has been to minimize the risk posed by desktop assets without sacrificing operational capability. The strategy they have employed is known as the Host Based Security System (HBSS). What is the DISA HBSS? HBSS is a suite of commercial-off-the-shelf (COTS) applications created by McAfee. In other words, HBSS is simply a program name crated by DoD.