Chapter 4 - Server, External Devices and Peripherals

8/8/2019 Chapter 4 - Server, External Devices and Peripherals

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CHAPTER 4 - SERVER, EXTERNALDEVICES AND PERIPHERALS


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Server computer definitionA servercomputer is a computer dedicated to

providing one or more services over a computernetwork

There are various types of server computer:

Application server

web server

E-mail server

SERVER


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Application server

A server program in a computer in a distributed network thatprovides the business logic for an application program.

Web server

A web server is a computer that stores websites and theirrelated files for viewing on the Internet.

E-mail server

A computer in a network that provides "post office" facilities. Itstores incoming mail for distribution to users and forwardsoutgoing mail through the appropriate channel.


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RAID

RAID stands forRedundant Array of InexpensiveDisks. A RAID system consists of two or moredisks working in parallel. They appear as one driveto the user, and offer enhanced performance orsecurity (or both).


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RAID Level

Level 0

Level 1

Level 2

Level 3

Level 4

Level 5

Level 6


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Advantages

RAID 0 offers great performance, both in read and

write operations.Th

ere is no overhead caused byparity controls.

All storage capacity can be used, there is no disk

overhead.

The technology is easy to implement.Disadvantages

RAID 0 is not fault-tolerant. If one disk fails, all data in

the RAID 0 array are lost. It should not be used on

mission-critical systems.Ideal useIdeal use

RAID 0 is ideal for non-critical storage of data that

have to be read/written at a high speed, e.g. on a

PhotoShop image retouching station.


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Data are stored twice by writing them to both the data disk (or set

of data disks) and a mirror disk (or set of disks) . If a disk fails, thecontroller uses either the data drive or the mirror drive for data

recovery and continues operation. You need at least 2 disks for a

RAID 1 array


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Advantages

RAID 1 offers excellent read speed and a write-speed. In case

a disk fails, data do not have to be rebuild, they just have to be

copied to the replacement disk.

Disadvantages

The main disadvantage is that the effective storage capacity is

only half of the total disk capacity because all data get writtentwice.

Ideal use/ Application

RAID-1 is ideal for mission critical storage, for instance for

accounting systems.


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EXTERNAL STORAGE DEVICES Tape Drive

- also known as a streamer, is a data storage devicethat reads and writes data stored on a magnetic tape.

Network-Attached Storage (NAS)

- is a file-level computer data storage connected to acomputer network providing data access toheterogeneous (not of the same kind) network clients.

Storage Area Network (SAN)

- is an enterprise-level storage network of several(often, hundreds of) hard drives managed by anintelligent device. If a drive crashes, your data is notlost


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Tape Drive


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Network-Attached Storage (NAS)


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Storage Area Networks (SAN)


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Storage Solution

Hot failover

- The backup is maintained at a location that isreasonably fast to access. Usually is a second disk

drive local to the machine.

IP based storage

-IP storage is a general term for several approaches tousing the Internet Protocol (IP) in a storage areanetwork (SAN) usually over Gigabit Ethernet.

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Chapter 4 - Server, External Devices and Peripherals