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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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