I'll try to explain again. Do not take this the wrong way, but you're completely unaware of how memory systems work. The OS requires a certain amount of memory address space to be reserved for itself. It reserves this space in volatile random access memory, which is quite fast. In notebooks and desktops it can also reserve more space in the form of virtual memory, although the way this is used is a bit different. Regardless of the presence of disk space used as virtual memory, it requires a minimum amount of contiguous address space in ram. Actually it goes further in that some values are simultaneously stored to the cpu cache. It accesses the values from ram on a cache miss. Both of these things are much faster than reading from disks, including ssds.