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Name :                       M.K.C Fernando

Subject :                    Information Systems
Infrastructure – CS112XX

Department :           Department of Computing And
Information Systems



Computer Network. 1

Advantages of Computer
Networks. 1

Disadvantages of Computer
Networks. 1

2.Advantages and
Disadvantages of e-mail 2

Advantages. 2

Disadvantages. 2

3.Client/Server Network
and VPN network. 3

a.      Client/server
computer Network. 3

b.      Virtual
Private Network. 3

c.      Disk cleanup. 4

d.      Disk
defragmenting. 4

e.      Backup. 5

4. Compare and contrast
the RAID Levels. 6

o       RAID 0 vs RAID 1. 6

o       RAID 0 vs RAID 2. 6

o       RAID 0 vs RAID 3. 7

o       RAID 0 vs RAID 4. 7

References. 8





1.Term Computer

Computer Network is simply a
collection of computers work together to perform a communication function with
each other. These computers are mostly connected via cabling(Ethernet cabling)
or via radio waves. These servers share resources like printers, file servers
etc. Examples for some computer networks are LAN(Local Area Network, WAN(Wide
Area Network), PAN(Personal Area Network), VPN(Virtual Private Network) etc..
Types of networks are categorized by characteristics like topology(eg: bus
topology, tree topology), protocol(for LAN, it is Ethernet), architecture(peer
to peer architecture or client server architecture).The computer networks are
used in sharing and transferring information so people should be aware of using
it effectively. They should know about the viruses and malwares which can
affect the system. 


Advantages of Computer Networks

a.     It makes the file sharing
more easier

b.     It allows more people to
get information they want in same time

c.      It is more flexible

d.     It increases storage

e.     It helps to costs

f.       It increases costs

g.     It helps in more
convenient resource sharing

Disadvantages of Computer Networks

a.     The system will be useless
if the main server breaks down

b.     The security problems are
arise because of the large number of users

c.      It lacks robustness

d.     It will gain more viruses
and malwares.

e.     It will promote illegal

f.       It requires highly skilled
person to handle for it,s operations and administration

g.     It needs highly costs set




and Disadvantages of e-mail


is easy to handle

            Email is a social media which we use
mostly in official mailing. It is very easy to use and clear. We can arrange
the messages as we wished. When you are already online it is free. We can keep
our mails safe and logical manner.

we have important, spam , sent mails, inbox like options we make us easy to
handle and save our time of finding different category mails.


has fastest speed

            From a second we can send a mail to
the other person . It is a great advantage in email as it save our time and the
receiver’s time. We can  also add a
subject of what we are sending and it makes receiver easily to understand the
content of the mail .

we can have multiple number of accounts. It is very easy to handle them with
multi handleing accounts.




As everyone widely using email, There may be so many
mails per a day. This mails can be most wanted or unwanted. Some mails may
cause threats to your computer the are called spam messages. It may cause new
viruses to your computer. To get rid of these viruses you have to install anti
virus guards which cost high.  


of personal inter relationships

            The mail which typed an sent through
email are not feel like our own hand written letter. So we are being lacking
idea about person day by day. It can not never beat a hand written card. We can
not express our true feelings by emailing .

Network and VPN network

a.     Client/server computer Network

network connects computers together. The computers are called clients and the
main computer is called the server. The server computer handles and manage the
applications and programs . Sharing application programs and files among client
side computers are also done by this server side computers. Mostly these kind
of computers handles databases. Some of the server side computers are mini
computers, mainframe computers which are highly powered work stations. The
client side computers are normally attached to the  Local Area Network(LAN).It provides the
graphical interface. They handles the presentation logics, processing logics
and storage logics.File server is manages file operations. This file server is
like a additional hard drive for all the computers in the system.

main difference about client side and server side computers are, the server
side computers are more storable and it has the highest speed than client side
computers. Some of the server machines are dedicated to do a specifics task
such as printing, managing etc. There is always a administrator to handle
server computer.

b.     Virtual Private Network

VPN, Virtual Private Network is a network which gives a safe and encrypted connection
even in a very unsecure network. The most common example for VPN is Internet.
As the VPN was developed because to remote users and office to access securely
applications and other resources. The VPN users use passwords, tokens to ensure
the safety. Some of the protocols used to secure was the IP secdurity(IP Sec),
Secure Socket Layer(SSL) and Transport Layer Security(TLS), Point to Point
Tunneling Protocol({{TS), Layer 2 Tunneling protocol(L2TP), OpenVPN.

are two types of VPN as Remote access VPN ,Site to Site VPN. The remote access VPN
uses public telecommunication infrastructure like internet to provide secure to
the organization’s network and  remote
users. This widely wants when people use public Wi-Fi hotpots. To secure its
connection it uses IP Sec and Secure Socket Layer. In Sie to Site VPN, it uses
gateway device to connect whole network to a one location. Most of this VPN
uses IP Sec. It also use carrier MLPS clouds as the transport of VPN rather tha
using internet for it.

c.      Disk cleanup

is a software made by Microsoft company for the better maintenance of a
computer in Windows 98 and all the windows came after that. It is a secure way
of deleting unwanted files and folders. It can also help in fastening computer
and make higher the performs of the computer. To maintain a good speed and
better performance , it should run the disk cleaner once a month. It can delete
temporary internet files.

different targeted file categories of disk cleanup are old files, temporary
windows files, internet files , downloaded program files, recycle bin, set up
log files, offline web pages etc.

cleanup is not only deleting unnecessary files but also it compressed files
together and it makes more free space in the hard drive. The access time of a
compressed file may differ from one computer to other.

d.     Disk defragmenting

defragmenting is the process of positioning of the non congruous data fragments
of data into which a computer file may be divided as it is stored in hard disk,
rearranging divide them in to small fragments. This disk defragmentation helps
to reduce the accessing time of data and makes the storage efficient manner. In
Windows 98, there came a tool called “system tool” comes with a built in tool
defragmentation. Windows 2000 came with a “light” version of Diskeeper
defragmentation. The Windows XP came with a utility called “disk defragmenter”.

understand what is disk defragmentation, first we have to have knowledge about
how a hard disk works, how a file system works and how a fragmentation really
happens. Hard disk contains moving parts, platters and write read head. Every
time we opened a file the signal goes to the CPU and it send it hard disk.
There is a myth that when defrags don’t touch your mouse. That is only a fear
in people minds. Safe mode defrag is not a harmful thing.


e.     Backup

Backup data is simply coping and archiving computer
data and it may used to restore the original after data loss.

 There are two
purposes of backup. The primary purpose is to recover the data loss by data
deletion or corruption. The data loss is a common experience when using a
computer. The secondary purpose is to recover data loss according to a user
defined retention policy.

 It is simply a
disaster recovery system and it should not be considered as full disaster
recovery plan. A backup system should have at least one copy of all data which
seems like important. It is not easy to organize storage space and management
of backup processes. The storage structure may use a data repository model in

There are many various types of data security storage
devices which are useful in backups and also there are many ways like provide
geographic redundancy, data security and portability.

Data Repository Method is the main strategy of
backups. These backup data should be stored and well organized. Example of
backup media is CDs.  There are two types
of repository data  as Unstructured, Full
Only(System imaging) and Reverse Delta. The full only again has two areas as
differential and incremental.

medias are hard disk, Magnetic tape, optical storage, solid state storage, remote
backup service, floppy disk etc. The magnetic tape is the most common medium
for bulk, backups. Some new tape drives are more faster than hard disks. The
hard disk is more competitive with magnetic tape. It is also a bulk storage
medium. Optical storage mediums are less powerful when comparing with tap or
hard disk. It has low speed and capacity. Ecordable CDs, DVDs and Blue-ray DVDs
are examples for optical storage. Sold Stste Storage has capacity than hard
disks but it is good for small volumes backups. It is more expensive than hard
disks. The remote backup service is getting popular because of broadband
internet access. Internet is slower than loal storage devices.





Compare and contrast the RAID Levels


RAID 0 vs RAID 1



Data is
distributed across the disks in the array.

All data
replicated on 2 disks

Lower than
single disk

Higher than
RAID 2,3,5 but lower than RAID 6

Lower than
single disk

higher than
single disk

Very high for
read and write

Twice similar
to single disk



RAID 0 vs RAID 2



Data is distributed across
the disks in the array.

Data is protected by
hamming codes.

No redundant information is

Redundant information
distributed across the number of disks

Lower than single disk

Much higher than single

Very high











RAID 0 vs RAID 3



Data is
distributed across the disks in the array.
No redundant
information is provided

Each data
sector is subdivided and distributed across all data disks.
data is normally stored on dedicated parity disk.

Lower than
single disk

Much higher
than single disk compared to RAID 2,4 or 5

Very high


Very high for
read and write

Twice similar
to single disk




RAID 0 vs RAID 4



Data is
distributed across the disks in the array.
No redundant
information is provided.

Data sectors
distributed as with disk striping
data is stored on dedicated parity disk.

Lower than
single disk

Much higher
than single disk compared to RAID 2,3, or 5

Very high

Similar to
disk striping

Very high for
read and write

Similar to
disk striping


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