There is no requirement to use the two components of DFS together; it is perfectly possible to use the logical namespace component without using DFS file replication, and it is perfectly possible to use file replication between servers without combining them into one namespace.
In 2016, the majority (51%) of the 8.4 million barrels per day (b/d) of crude oil produced in the Lower 48 states was light oil, or less dense oil with an API gravity of 40.1 or above. Light oil also made up more than half of the oil produced in 2015. API gravity is measured as the inverse of the density of a petroleum liquid relative to water. The higher the API gravity, the lower the density of the petroleum liquid, so light oils have high API gravities.
There are four types of crude oil: Class A: Light, Volatile Oils: These oils are highly fluid and highly toxic to humans, and include jet fuel and gasoline. Class B: Non-Sticky Oils: These oils are waxy and less toxic to humans, and include diesel fuel and light crude oil. Class C: Heavy, Sticky Oils: These oils are brown or black and sticky or tarry, and include most crude oils. Their toxicity is low, but if spilled, their impacts on waterfowl and wildlife can be severe.