Open main menu

A distributed data store is a computer network where information is stored on more than one node, often in a replicated fashion.[1] It is usually specifically used to refer to either a distributed database where users store information on a number of nodes, or a computer network in which users store information on a number of peer network nodes.

Distributed databasesEdit

Distributed databases are usually non-relational databases that enable a quick access to data over a large number of nodes. Some distributed databases expose rich query abilities while others are limited to a key-value store semantics. Examples of limited distributed databases are Google's Bigtable, which is much more than a distributed file system or a peer-to-peer network,[2] Amazon's Dynamo[3] and Windows Azure Storage.[4]

As the ability of arbitrary querying is not as important as the availability, designers of distributed data stores have increased the latter at an expense of consistency. But the high-speed read/write access results in reduced consistency, as it is not possible to have both consistency, availability, and partition tolerance of the network, as it has been proven by the CAP theorem.

Peer network node data storesEdit

In peer network data stores, the user can usually reciprocate and allow other users to use their computer as a storage node as well. Information may or may not be accessible to other users depending on the design of the network.

Most peer-to-peer networks do not have distributed data stores in that the user's data is only available when their node is on the network. However, this distinction is somewhat blurred in a system such as BitTorrent, where it is possible for the originating node to go offline but the content to continue to be served. Still, this is only the case for individual files requested by the redistributors, as contrasted with networks such as Freenet, Winny, Share and Perfect Dark where any node may be storing any part of the files on the network.

Distributed data stores typically use an error detection and correction technique. Some distributed data stores (such as Parchive over NNTP) use forward error correction techniques to recover the original file when parts of that file are damaged or unavailable. Others try again to download that file from a different mirror.

ExamplesEdit

Distributed non-relational databasesEdit

Product License High availability Notes
Apache Accumulo AL2
Aerospike AGPL
Apache Cassandra AL2 Yes formerly used by Facebook
Apache Ignite AL2
Bigtable Proprietary used by Google
Couchbase Proprietary used by LinkedIn, PayPal, and eBay
CrateDB AL2 Yes
Druid (open-source data store) AL2 used by Netflix, and Yahoo
Dynamo Proprietary used by Amazon
Hazelcast AL2, Proprietary
HBase AL2 formerly used by Facebook
Hypertable GPL 2 Baidu
MongoDB custom
Riak AL2 Yes
Scylla AGPL
Voldemort AL2 used by LinkedIn

Peer network node data storesEdit

See alsoEdit

ReferencesEdit

  1. ^ Yaniv Pessach, Distributed Storage (Distributed Storage: Concepts, Algorithms, and Implementations ed.)
  2. ^ "Bigtable: Google's Distributed Data Store". http://the-paper-trail.org/: Paper Trail. Archived from the original on 2017-07-16. Retrieved 2011-04-05. Although GFS provides Google with reliable, scalable distributed file storage, it does not provide any facility for structuring the data contained in the files beyond a hierarchical directory structure and meaningful file names. It’s well known that more expressive solutions are required for large data sets. Google’s terabytes upon terabytes of data that they retrieve from web crawlers, amongst many other sources, need organising, so that client applications can quickly perform lookups and updates at a finer granularity than the file level. [...] The very first thing you need to know about Bigtable is that it isn’t a relational database. This should come as no surprise: one persistent theme through all of these large scale distributed data store papers is that RDBMSs are hard to do with good performance. There is no hard, fixed schema in a Bigtable, no referential integrity between tables (so no foreign keys) and therefore little support for optimised joins.
  3. ^ Sarah Pidcock (2011-01-31). "Dynamo: Amazon's Highly Available Key-value Store" (PDF). http://www.cs.uwaterloo.ca/: WATERLOO – CHERITON SCHOOL OF COMPUTER SCIENCE. p. 2/22. Retrieved 2011-04-05. Dynamo: a highly available and scalable distributed data store
  4. ^ "Windows Azure Storage". 2011-09-16. Archived from the original on 9 November 2011. Retrieved 6 November 2011.