https://www.bigdataschool.ru/blog/hdfs-%d0%bf%d1%80%d0%b8%d0%bd%d1%86%d0%b8%d0%bf%d1%8b-%d1%80%d0%b0%d0%b1%d0%be%d1%82%d1%8b-%d0%b2-big-data.html