Parallel database
Encyclopedia
A parallel database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...

system seeks to improve performance through parallelization of various operations, such as loading data, building indexes and evaluating queries. Although data may be stored in a distributed fashion, the distribution is governed solely by performance considerations. Parallel databases improve processing and input/ouput speeds by using multiple CPUs and disks in parallel. Centralized and client–server database systems are not powerful enough to handle such applications. In parallel processing, many operations are performed simultaneously, as opposed to serial processing, in which the computational steps are performed sequentially.

Parallel databases can be roughly divided into two groups, the first group of architecture is the multiprocessor architecture, the alternatives of which are the followings :
  • Shared memory architecture, where multiple processors
    Central processing unit
    The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

     share the main memory space, as well as mass storage (e.g. hard disk drives).
  • Shared disk architecture, where each node has its own main memory, but all nodes share mass storage, usually a storage area network
    Storage area network
    A storage area network is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices...

    . In practice, each node usually also has multiple processors.
  • Shared nothing architecture
    Shared nothing architecture
    A shared nothing architecture is a distributed computing architecture in which each node is independent and self-sufficient, and there is no single point of contention across the system...

    , where each node has its own mass storage as well as main memory.


The other architecture group is called hybrid architecture, which includes:
  • Non-Uniform Memory Architecture (NUMA), which involves the Non-Uniform Memory Access
    Non-Uniform Memory Access
    Non-Uniform Memory Access is a computer memory design used in Multiprocessing, where the memory access time depends on the memory location relative to a processor...

    .
  • Cluster (shared nothing + shared disk: SAN/NAS), which is formed by a group of connected computers.
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