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Redundant Array of Inexpensive Servers

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Redundant Array of Inexpensive Servers (RAIS) is the use of multiple servers to provide the same service in such a way that service will still be available if the servers fails. The term may imply some kind of load balancing between the servers.

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Ia a simple, high performance, mainframe-grade alternative to today’s Enterprise computing infrastructure solutions. Te RAIS, turn an array of ordinary servers into a single virtual machine like RAID 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 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 the invention of a radical new memory management system called Versioned Memory.

RAIS provide the benefits of an SMP at the entry cost of clusters.

How does RAIS work.

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 very high cost SMP architectures. RAIS (“Redundant Array of Inexpensive Servers”) achieves this by turning a cluster of independent servers into a single large server running applications across a virtualised network of nodes. RAIS does the same for cluster based network management and will have the same far reaching consequences across the world of enterprise computing. RAIS models for servers the same capability as RAID does for disks, offering variations of scale and redundancy depending on the configuration chosen.

Therefore, just as 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 Symmetric Multiprocessor (SMP) system.

What does RAIS provide?

The main significant benefit is the substantial reduced capital cost providing an alternative solution to migrating to SMP.

  • Scalability: applications can be scaled up without the need for expensive re-coding and reconfiguration.
  • Resilience. Continuous application operation even in the event of multiple server or component failure, automatically continuing application execution on surviving servers transparently to the application.
  • Compatibility. Full binary compatibility with any SMP architecture; applications automatically and transparently avail themselves of RAIS capability without any source-code or object-code changes.
  • Heterogeneity. Ability to cluster different configurations of servers, either by memory type or even by processor type.
  • Low impact on existing staff skill requirements. Is easily assimilated into existing daily operations so developer teams are left to concentrate on their specific applications, having no need to worry about dealing with operating code and scalability issues.
  • Uninterrupted change out of servers. Directs workloads away from a failed server, but it enables the hot swapping of hardware without interruption to the operation of an application.
  • Increase IT flexibility and agility. Network configurations can be easily adjusted to suit peaks of operation.
  • Reduced power and cooling consumption. The x86 servers have much reduced power demands compared to SMP hardware.

    • References

    Redundant Array of Inexpensive Servers Wikipedia
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