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http://www.agildata.com/database-sharding/
The Rise of Database Sharding
The concept of Database Sharding has been gaining popularity over the past several years, due to the enormous growth in transaction volume and size of business application databases. This is particularly true for many successful online service providers, Software as a Service (SaaS) companies, and social networking Web sites.
Database Sharding can be simply defined as a “shared-nothing” partitioning scheme for large databases across a number of servers, enabling new levels of database performance and scalability achievable. If you think of broken glass, you can get the concept of sharding – breaking your database down into smaller chunks called “shards” and spreading those across a number of distributed servers.
The term “sharding” was coined by Google engineers, and popularized through their publication of the Big Table architecture. However, the concept of “shared-nothing” database partitioning has been around for a decade or more and there have been many implementations over this period, especially high profile in-house built solutions by Internet leaders such as eBay, Amazon, Digg, Flickr, Skype, YouTube, Facebook, Friendster, and Wikipedia.
The focus of this paper is on the need for Database Sharding, the options available for database partitioning, and the key considerations for a successful sharding implementation.