It is right, you don’t read the title wrong. In most people’s mind, Hadoop was almost a synonym of Big Data. Adding the magic word to your resume means more opportunities and higher pay. How possible is its future misty? Let’s get things clear together. Continue reading
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NoSQL (Not Only SQL) database, departing from relational model, is a hot term nowadays although the name is kind of misleading. The data model (e.g., key-value, document, or graph) is surely very different from the tabular relations in the RDBMS. However, these non-relational data models are actually not new. For example, BerkeleyDB, a key-value store, was initially released in 1994 (20 years ago). In the web and social network era, the motivations of (distributed) NoSQL movement are mainly towards to horizontal scaling and high availability. By playing with the CAP theorem, many NoSQL stores compromise consistency in favor of availability and partition tolerance, which also brings the simplicity of design. Note that a distributed database system doesn’t has to drop consistency. For instance, TeraData and Google’s F1 are ACID-compliant (Atomicity, Consistency, Isolation, Durability). However, it makes systems much more complicated and also imposes high performance overhead. Continue reading