Even more elementary that sibling comments, this also happens in gaming all the time. You are recording live results, say in Fifa, but if you unplug your device

Even more elementary that sibling comments, this also happens in gaming all the time. You are recording live results, say in Fifa, but if you unplug your device, your results are gone, since they were memory only. The game simply cannot afford to write to disk, the write is "non guaranteed" in the true sense of the word, but it is fast. You then "checkpoint" when the game is over. You might dissent that is not a "non-guaranted" write, because in fact the write did occur, but I simply want to allude to the concept of a "non-secured" write, in that it vanished without an fsync.