![]() ![]() When a machine runs out of system memory, it compresses some tablets using Google proprietary compression techniques (BMDiff and Zippy). Tables are stored as immutable SSTables and a tail of logs (one log per machine). Also, if a machine goes down, a tablet may be spread across many other servers so that the performance impact on any given machine is minimal. ![]() If one table is receiving many queries, it can shed other tablets or move the busy table to another machine that is not so busy. It also allows for fine-grained load balancing. This setup allows tablets from a single table to be spread among many servers. A tablet is around 200 MB, and each machine saves about 100 tablets. In order to manage the huge tables, Bigtable splits tables at row boundaries and saves them as tablets. The time stamp allows for operations such as "select 'n' versions of this Web page" or "delete cells that are older than a specific date/time." There can be multiple versions of a cell with different time stamps. Tables consist of rows and columns, and each cell has a time stamp. Each table is a multidimensional sparse map. It does not support joins nor does it support rich SQL-like queries. tables are optimized for GFS (Google File System) by being split into multiple tablets - segments of the table as split along a row chosen such that the tablet will be ~200 megabytes in size.īigTable is not a relational database.each table has multiple dimensions (one of which is a field for time, allowing versioning).it is easy to add more machines to the system and automatically start taking advantage of those resources without any reconfiguration.it works across hundreds or thousands of machines.designed to scale into the petabyte range.a sparse, distributed multi-dimensional sorted map, sharing characteristics of both row-oriented and column-oriented databases. ![]() System (built by Google) for managing structured data A Distributed Storage System for Structured Data ![]()
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