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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. :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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Redundant Array of Inexpensive Servers」の詳細全文を読む スポンサード リンク
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