"History of Science Fiction" is a graphic chronology that maps the literary genre from its nascent roots in mythology and fantastic stories to the somewhat calcified post-Star Wars space opera epics of today. The movement of years is from left to right, tracing the figure of a tentacled beast, derived from . Wells' War of the Worlds Martians. Science Fiction is seen as the offspring of the collision of the Enlightenment (providing science) and Romanticism, which birthed gothic fiction, source of not only SciFi, but crime novels, horror, westerns, and fantasy (all of which can be seen exiting through wormholes to their own diagrams, elsewhere). Science fiction progressed through a number of distinct periods, which are charted, citing hundreds of the most important works and authors. Film and television are covered as well.
HDFS is designed to reliably store very large files across machines in a large cluster. It stores each file as a sequence of blocks; all blocks in a file except the last block are the same size. The blocks of a file are replicated for fault tolerance. The block size and replication factor are configurable per file. An application can specify the number of replicas of a file. The replication factor can be specified at file creation time and can be changed later. Files in HDFS are write-once and have strictly one writer at any time. The NameNode makes all decisions regarding replication of blocks. HDFS uses rack-aware replica placement policy. In default configuration there are total 3 copies of a datablock on HDFS, 2 copies are stored on datanodes on same rack and 3rd copy on a different rack.