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.
API stands for the American Petroleum Institute, which is the major United States trade association for the oil and natural gas industry. The API represents about 400 corporations in the petroleum industry and helps to set standards for production, refinement, and distribution of petroleum products.