A Redundant Array of Inexpensive Servers (RAIS) or Redundant Array of Independent Nodes (RAIN) is the use of multiple
servers to maintain service if one server fails. This is similar in concept to how
RAID
RAID (; redundant array of inexpensive disks or redundant array of independent disks) is a data storage virtualization technology that combines multiple physical Computer data storage, data storage components into one or more logical units for th ...
turns a cluster of ordinary disks into a single block device. RAIS was designed to provide the benefits of a
symmetric multiprocessor system
Symmetric multiprocessing or shared-memory multiprocessing (SMP) involves a multiprocessor computer hardware and software architecture where two or more identical processors are connected to a single, shared main memory, have full access to all ...
(SMP) at the entry cost of
computer cluster
A computer cluster is a set of computers that work together so that they can be viewed as a single system. Unlike grid computers, computer clusters have each node set to perform the same task, controlled and scheduled by software. The newes ...
s.
The term may imply some kind of
load balancing between the servers.
Technology
RAIS is a simple, high performance, mainframe-grade alternative to more expensive enterprise computing infrastructure solutions. It turns an array of ordinary servers into a single virtual machine, similar in concept to how
RAID
RAID (; redundant array of inexpensive disks or redundant array of independent disks) is a data storage virtualization technology that combines multiple physical Computer data storage, data storage components into one or more logical units for th ...
turns a cluster of ordinary disks into a single block device. Every RAIS node is a stateless computing unit. RAIS stripes and mirrors
application code
This glossary of computer science is a list of definitions of terms and concepts used in computer science, its sub-disciplines, and related fields, including terms relevant to software, data science, and .
A
...
and memory across an array of ordinary servers using the standard RAID schemata of level 0, level 1, level 5, level 1+0. This is possible through a memory management system called Versioned Memory.
Data blocks of each stream are striped across the array servers. A fast packet switch is used to connect server and client stations. Each server has a dedicated network segment, and each client contacts the server one by one. Each server has its own storage, CPU, and network segment. The server capacity increases with the number of servers.
In a manner more usually associated with high cost SMP architectures, RAIS achieves this by turning a cluster of independent servers into a single large server running applications across a virtualised network of nodes. The concept is similar to how RAID stripes and mirrors data across multiple independent disks and code of an application program across multiple independent nodes of a cluster. The applications see only a single logical shared memory which functions as a binary compatible SMP system.
If the data is split into segments and distributed between multiple storage providers, the technology has applications for improving confidentiality in cloud computing.
See also
*
Disk array controller
A disk array controller is a device that manages the physical disk drives and presents them to the computer as logical units. It often implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides additio ...
*
Disk Data Format (DDF)
*
Vinum volume manager
Vinum is a logical volume manager, also called software RAID, allowing implementations of the RAID-0, RAID-1 and RAID-5 models, both individually and in combination. The original Vinum was part of the base distribution of the FreeBSD operating ...
References
Servers (computing)
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