Defragmenting is Packing a Suitcase

Imagine the storage device is a suitcase. When we pack, when we add something new, we put something into the suitcase. We might also remove something, which is the opposite: we are pulling something out of the suitcase.

Here is a problem we often have: what if we want to add one more big object into the suitcase? We know that the suitcase has enough space to hold it, we have already pulled enough stuff out. The trouble is the space we need is spread out randomly in the suitcase.

What should we do? Reorganize the suitcase! Bingo! This is the time and the reason we need to defragment our storage device as well!