Revision as of 15:52, 10 December 2017

(description mass storage system)

Types

Virtual disks

A method of expanding the program-addressable online storage of a single computer. The well-known counterpart of virtual disk, virtual memory operates on the basic mechanism of a page fault and provides an indefinately large address space for programs executing in a host computer. A virtual disk is useful for a single computer whose existing disk space is becoming exhausted and where it is uneconomical to keep adding more and more disks. With special software, this device can be used to transparently extend the local online disk space.

Network file server

A network file server supplies network users with large and cheap storage space. Some file servers use only magnetic disk; others use a storage hierarchy transparently managed by special software running on a control computer. The file server consists of fast-staging storage and large secondary, archive storage. Staging storage is online disk. It can be implemented through parallel disk arrays and software disk striping. Archive storage is usually implemented through tape. Network file servers can be attached to more than one network. There are four categories of file servers:

PC LANs ( local area networks; one to several gigabytes), workstation LANs (tens of gigabytes), departmental minis or minisupers ( a few hundred gigabytes), and large mainframes or supercomputers ( one to tens of terabytes) In all cases, server is a shared network resource rather than being attached to one workstation or one computer because it provides cheap storage for many network users.

The file server

A file server is a repository in which data must be kept safely and indefinitely. For example, seismic data and earth observation data collection by satellites are generally kept in a file archive. The emphasis in a file archive is on low cost of storage and high reliability. The media used in a file archive must be stable over time, economical and reasonably fast. The archives are implemented by the traditional tape library. This system can in many cases be replaced by devices and software which form a more effective new storage system.

Automated network storage management

The strategy used in this case is similar to the file server. A network file server is a large and fast device because frequently accessed user files are cached on its fast disk. Infrequently used files are stored on tape. It has been shown that over 80% of the data in the system may be removed from expensive online storage without significantly sacrificing performance.

Network file backup

The backup problem has become particularly acute with the growing use of networked computing. With so many users on a network, it is impractical to require each one to be responsible for the backup of his data. Network-wide backup is considered a mass storage application simply because networks have so many users and the amount of data to backup is so large. The use of common network resources, such as a computer server, a file server, suggests a common network-wide backup server.

Evolution

Prices in the market

The traditional hard disks have not stopped offering any more and better services since its journey began on the market, and nowadays the capacities and prices of these units have gone fitting up to coming at a level in which the cost for GB is almost ridiculous.

This way, a unit of 2 TB of Digital Western can be for 89,99 dollars in the United States, and that gives a cost for 0,043 dollars for GB. Or what is the same, scarcely 3 cents for GB, a number that makes clear the complex margins in which these units move.

Links to online shops (U.K and U.S)

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