The term Big Data is an all-encompassing phrase that has various subdivisions addressing different needs of the customers. The most common description of Big Data talks about the four V’s: Volume, Velocity, Variety and Veracity.
Volume represents terabytes to exabytes of data, but this is data at rest. Velocity talks about streaming data requiring milliseconds to seconds of response time and is about data in motion. Variety is about data in many forms: structured, unstructured, text, spatial, and multimedia. Finally, veracity means data in doubt arising out of inconsistencies, incompleteness and ambiguities.
Hadoop is the first commercial version of Internet-scale supercomputing, akin to what HPC (high-performance computing) has done for the scientific community. It performs, and is affordable, at scale. No wonder it originated with companies operating at Internet scale, such as Yahoo in the 1990s, and then at Google, Facebook and Twitter.
In the scientific community, HPC was used for meteorology (weather simulation) and for solving engineering equations. Hadoop is used more for discovery and pattern matching. The underlying technology is similar: clustering, parallel processing and distributed file systems. Hadoop addresses the “volume” aspect of Big Data, mostly for offline analytics.
NoSQL products such as MongoDB address the “variety” aspect of Big Data: how to represent different data types efficiently with humongous read/write scalability and high availability for transactional systems operating in real time. The existing RDBMS solutions are inadequate to address this need with their schema rigidity and lack of scale-out solutions at low cost. Therefore, Hadoop and NoSQL are complementary in nature and do not compete at all.
Whether data is in NoSQL or RDBMS databases, Hadoop clusters are required for batch analytics (using its distributed file system and Map/Reduce computing algorithm). Several Hadoop solutions such as Cloudera’s Impala or Hortonworks’ Stinger, are introducing high-performance SQL interfaces for easy query processing.
Hadoop’s low cost and high efficiency has made it very popular. As an example, Sears’ process for analyzing marketing campaigns for loyalty club members used to take six weeks on mainframe, Teradata and SAS servers. The new process running on Hadoop can be completed weekly.
The Hadoop systems, at 200TB, cost about one-third of 200TB relational platforms. Mainframe costs have been reduced by more than US$500,000 per year while delivering 50x to 100x better performance on batch jobs. The volume of data on Hadoop is currently at 2PB. Sears uses Datameer, a spreadsheet-style tool that supports data exploration and visualization directly on Hadoop. It claims to develop interactive reports in three days, a process that use to take six to 12 weeks.