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Graduate Diploma

Level 7

(Information Technology Strand)

STD711 Networing and !peratingSy"tem

(N!S#$""ignment)

$""ignment 1%inal &e"ult' $""e""or

Signature

StudentName

Dhiraj Pahuja Nikhil ChaithanyaPravin

Kumar

Student ID

  TIZ0000262  TIZ00001UD TIZ00001U

8StudentSignature

$""e""or

  Tamanna Phogat

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Task 1. Define multi-user operating system. Describe four functional features of multi-

user operating systems from different vendors e.g. Windows, Linux, !"# and $ac %&

&olution. Multi-user operating system is a computer operating system (OS) that allows

multiple users on different computers or terminals to access a single system with one OS on

it. These programs are often quite complicated and must be able to properly manage the

necessary tasks required by the different users connected to it. The users will typically be at

terminals or computers that gie them access to the system through a network! as well as

other machines on the system such as printers. " multi-user operating system differs from a

single-user system on a network in that each user is accessing the same OS at different

machines.

'unctional 'eatures of nix

• multi-user#-more than one user can use the machine at a time

supported ia terminals (serial or network connection)

• multi-tasking#-more than one program can be run at a time

• hierarchical directory structure#- to support the organisation and maintenance of files

•  portability#- only the kernel ( $%&') written in assembler 

tools for program deelopment a wide range of support tools (debuggers! compilers)

'unctional feature of linux

• Multiuser apability# This is a capability of inu* OS where! the same computer 

resources + hard disk! memory! etc. are accessible to multiple users. Of course! not on

a single terminal! they are gien different terminals to operate from. " terminal will

consist of at least a Monitor,/! keyboard and mouse as input deices. "ll the

terminals are then connected to the main inu* Serer or 0ost Machine! whose

resources and connected peripheral deices such as printer! can be used.

• Multitasking# inu* has the ability to handle more than one 1ob at a time! say for 

e*ample you hae e*ecuted a command for sorting for a huge list and simultaneouslytyping in a notepad. This is managed by diiding the 2/ time intelligently by the

implementation of scheduling policies and the concept of conte*t switching.

• 2ortability# 2ortability was the one of the main features that made inu* so popular 

among the users! but portability doesn3t mean that it is smaller in file si4e and can be

carried on pen drie! s and memory cards. 5nstead! here portability means that

inu* OS and its application can work on different types of hardwares in the same

way. inu* kernel and application programs support their installation een on ery

least hardware configuration.

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• Security# Security is a ery important part of any OS! for the organi4ations,user who

is using the system for their confidential works! inu* does proide seeral security

concepts for protecting their users from unauthori4ed access of their data and system.

'unctional 'eatures of Windows(

%. 6nabling startup application programs. Thus! the operating system must hae#

- " te*t editor 

- " translator 

- "n editor of links

7. The allocation of resources needed to e*ecute programs is done by identifying# the

 programs that are running! the need for memory! peripheral deices and data protection

requirements.

8. 9acilities for data compression! sorting! mi*ing! cataloging and maintenance of libraries!

through utility programs aailable.

:. 2lan implementation works according to certain criteria! for efficient use of central

 processing unit.

;. "ssisting implementation of programs through computer-user communication system! at

 both hardware and software leel.

'eatures %f $)*(-

 &ecurity#-Mac OS < includes arious security features! serices! and "25s (including what=s

aailable on typical >ni* systems)! such as those for controlling,managing passwords!

certificates! public,priate keys! application-leel priileged operations (capabilities)! trust

 policies! etc. Mac OS < supports ?erberos! OpenSS! and 2"M as well.

root login is disabled by default! and sudo is used for administratie access. @ou can

use ,usr,bin,security from the command line to control the security framework 

+ower $anagement  #-M" OS < in con1unction with Macintosh hardware make up for 

some impressie power and thermal management. The four independently controlled thermal

4ones and the nine fans of the 2ower Mac A; hae been discussed aplenty. Mac OS <

includes driers and other logic for the 7% temperature sensors in that machine. The

2owerBooks hae sophisticated thermal management as well. @ou can =grep -i= for CthermalC

and CtemperatureC in the output of =ioreg -l=on Mac OS < for related miscellaneous

information.

Based on power,thermal feedback! processor and bus speeds can be reduced to consere

 power and control heat. "ll current "pple notebook batteries hae remaining charge

indicators. On the 2owerBooks! you can change the battery without powering-off courtesy an

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internal backup battery that holds charge for a few minutes. Dote that you do need to put the

machine to sleep to do this.

Devices- "pple has e*cellent support for 9ireEire deices! hardly surprising since they

inented 9ireEire. @ou can readily boot from e*ternal dries! treat a Mac to behae as if it

were an e*ternal 9ireEire drie (boot it with the T key pressed! which puts the computer 

in Target Disk Mode)! and een connect two computers together using T2,52 oer a

9ireEire cable. The iSight and the i2od use 9ireEire connections too.

"pple has also been pushing Bluetooth with their newer computers! although you can get

adapters for older models. 5n addition to using Bluetooth for communicating with phones and

2"s! "pple also uses it for their wireless keyboard and mouse! which are ery well

designed and work well with Mac OS <.

Data and "nformation $anagement(- Ehile not really /topian! Mac OS < makes a ery

good attempt at keeping arious data and information organi4ed by conte*t! rather than

haing files strewn all oer the place. System and "pplication CpreferencesC can be global

(system-wide) or per-user! and are kept organi4ed as such. The arious "25s make sure that

(if used properly)! all of a user=s data is stored deterministically.

One of the most useful features of Mac OS < is its support for  synchronization of your 

computer=s configuration! or personality! if you will. urrently this data set includes the

address book! calendar! and Safari bookmarks! although "pple should add more entities. 5f 

you are doing a new installation or clean upgrade of your system! it is a boon to hae the

following# on the ColdC installation! click a button to synchroni4e the aboe information to a

deice! which can be your i2od! or your .Mac account. On the CnewC machine! you can

reerse synchroni4e and hae this information in1ected.

Task 1.1 Describe te purpose of te following components of a multi-user operating

system

1. +rocess management

. $emory management

. +rocessor management

/. &torage management

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Wat ardware or0and software modules are involved wit tese

components in te computer system.

&olution 1.1.

+rocess $anagement(- 2rocess management is an integral part of any modern-day operating

system .The OS must allocate resources to processes! enable processes to share and e*change

information! protect the resources of each process from other processes and enable

synchronisation among processes. To meet these requirements! the OS must maintain a data

structure for each process! which describes the state and resource ownership of that process!

and which enables the OS to e*ert control oer each process.

$emory $anagement(- Memory management refers to management of 2rimary Memory or Main Memory. Main memory is a large array of words or bytes where each word or byte has

its own address. Main memory proides a fast storage that can be access directly by the 2/.

So for a program to be e*ecuted! it must in the main memory. Operating System does the

following actiities for memory management.

 • ?eeps tracks of primary memory i.e. what part of it are in use by whom! what part are not

in use.

 • 5n multiprogramming! OS decides which process will get memory when and how much.

• "llocates the memory when the process requests it to do so. • e-allocates the memory when the process no longer needs it or has been terminated.

+rocessor $anagement(-  5n multiprogramming enironment! OS decides which process

gets the processor when and how much time. This function is called process scheduling.

Operating System does the following actiities for processor management.

• ?eeps tracks of processor and status of process. 2rogram responsible for this task is known

as traffic controller.

• "llocates the processor (2/) to a process.

• e-allocates processor when processor is no longer required

&torage $anagement(- Memory management refers to management of 2rimary Memory or 

Main Memory. Main memory is a large array of words or bytes where each word or byte has

its own address. Main memory proides a fast storage that can be access directly by the 2/.

So for a program to be e*ecuted! it must in the main memory. Operating System does the

following actiities for memory management.

 • ?eeps tracks of primary memory i.e. what part of it are in use by whom! what part are not

in use.• 5n multiprogramming! OS decides which process will get memory when and how much.

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• "llocates the memory when the process requests it to do so.

• e-allocates the memory when the process no longer needs it or has been terminated.

0ardware or,and software modules are inoled with these components in the computer 

system

Device manager (-  The Device $anager is a ontrol 2anel applet in Microsoft

Eindows operating systems. 5t allows users to iew and control the hardware attached to the

computer. Ehen a piece of hardware is not working! the offending hardware is highlighted

for the user to deal with. The list of hardware can be sorted by arious criteria.

0ard isk#- " ard disk drive (DD)! ard disk ! ard drive or fixed disk  is a data storage

deice used for storing and retrieing digital information using one or more rigid (ChardC)

rapidly rotating disks ( platters) coated with magnetic material. The platters are paired

with magnetic heads arranged on a moing actuator  arm! which read and write data to the

 platter surfaces.F7G ata is accessed in a random-access manner! meaning that

indiidual blocks of data can be stored or retrieed in any order rather than sequentially.

0s retain stored data een when powered off.

  2)$(-  2andom-access memory (2)$ ,rHm,) is a form of computer data storage.  "random-access memory deice allowsdata items to be accessed (read or written) in almost the

same amount of time irrespectie of the physical location of data inside the memory. 5n

contrast! with other direct-access data storage media such as hard disks! -IEs! -

IEs and the older  drum memory! the time required to read and write data items aries

significantly depending on their physical locations on the recording medium! due to

mechanical limitations such as media rotation speeds and arm moement delays

Task - *oose two different operating systems from different vendors e.g. Windows,

Linux, !"# and $ac %&, analyse and discuss ow te following functions are

implemented in selected multi-user operating systems( process management, memory

management, processor management, and storage management.

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Solution#

+rocess $anagement "n Linux

There are two kinds of e*ecution conte*ts in inu*. 2rocess and lightweight processes.

0oweer! inu* makes no distinction among these forms from scheduling point of iew.

inu* uses lightweight processes to proide the features of a multithreaded application. The

inu* kernel use to store information about each process in the process descriptor. Ehich is

implemented as taskJstruct.

+rocess Descriptor(

fig %.%# 2rocess escriptor 

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+rocess &tate(

uring the lifecycle of a process! process can migrate into a number of states. 6ach

state describes particular properties of a process at that instant by means of some attributes.

These attributes are defined in the process descriptor. "n array of flags is used to describe the

state of a process. These states are mutually e*clusie! any process can be in one of these

states at a particular time. 6ach state is represented by a flag in the state! which is set. "ll

other flags are cleared. ifferent possible states of a process are as follows.

T"S?JI/DD5DA

" process is either running or is ready to run.

T"S?J5DT6II/2T5B6

The process is blocked on a particular eent! but it can wake up by deliering a signal to it

"n eent can be input from user! disk 5,O etc. On wake up it gets it state back toT"S?JI/DD5DA.

T"S?J/D5DT6II/2T5B6

5n this state also the process is blocked! but it cannot be interrupted by deliering a signal to

it. 5f at all it gets a signal it ignores it.

$emory management "n linux(-

The memory management subsystem is one of the most important parts of the operating

system.

Since the early days of computing! there has been a need for more memory than e*ists

 physically in a system. Strategies hae been deeloped to oercome this limitation and the

most successful of these is irtual memory. irtual memory makes the system appear to hae

more memory than it actually has by sharing it between competing processes as they need

it.irtual memory does more than 1ust make your computer=s memory go further. The

memory management subsystem proides#

Large )ddress &paces(- The operating system makes the system appear as if it has a larger 

amount of memory than it actually has. The irtual memory can be many times larger than

the physical memory in the system.6ach process in the system has its own irtual address

space. These irtual address spaces are completely separate from each other and so a process

running one application cannot affect another. "lso! the hardware irtual memory

mechanisms allow areas of memory to be protected against writing. This protects code and

data from being oerwritten by rogue applications.

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$emory $apping(- Memory mapping is used to map image and data files into a processes

address space. 5n memory mapping! the contents of a file are linked directly into the irtual

address space of a process.

'air +ysical $emory )llocation(-The memory management subsystem allows each

running process in the system a fair share of the physical memory of the system! Shared

irtual Memory

"lthough irtual memory allows processes to hae separate (irtual) address spaces! there are

times when you need processes to share memory. 9or e*ample there could be seeral

 processes

in the system running the bash command shell. Iather than hae seeral copies of bash! one

in

each processes irtual address space! it is better to hae only one copy in physical memory

and all of the processes running bash share it. ynamic libraries are another common

e*ample of 

e*ecuting code shared between seeral processes.Shared memory can also be used as an 5nter 

2rocess ommunication (52) mechanism! with two or more processes e*changing

information ia memory common to all of them. inu* supports the /ni* TM System

shared memory 52.

&torage $anagement "n Linux(- Storage management system deals with allocating and

freeing pages! groups of pages! and small blocks of memory.  ν 5t has additional mechanisms

for handling irtual memory! memory mapped into the address space of running processes.  ν

Splits memory into 8 different 4ones due to hardware characteristics

+rocess management in windows

+rocess management is an integral part of any modern-day operating system (OS). The OS

must allocate resources to processes! enable processes to share and e*change information!

 protect the resources of each process from other processes and enable synchronisation among

 processes. To meet these requirements! the OS must maintain a data structure for each

 process! which describes the state and resource ownership of that process! and which enables

the OS to e*ert control oer each process.

$emory management "n windows

Memory management is the functionality of an operating system which handles or manages

 primary memory. Memory management keeps track of each and eery memory location

either it is allocated to some process or it is free. 5t checks how much memory is to be

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allocated to processes. 5t decides which process will get memory at what time. 5t tracks

wheneer some memory gets freed or unallocated and correspondingly it updates the status.

Memory management proides protection by using two registers! a base register and a limit

register. The base register holds the smallest legal physical memory address and the limit

register specifies the si4e of the range. 9or e*ample! if the base register holds 8&&&&& and

the limit register is %7&K&&&! then the program can legally access all addresses from 8&&&&&

through :%%KKK.

5nstructions and data to memory addresses can be done in following ways

• *ompile time -- Ehen it is known at compile time where the process will reside!

compile time binding is used to generate the absolute code.

• Load time -- Ehen it is not known at compile time where the process will reside in

memory! then the compiler generates re-locatable code.

• 3xecution time -- 5f the process can be moed during its e*ecution from one

memory segment to another! then binding must be delayed to be done at run time

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&torage management in windows

Storage management is ery closely related to Storage Iesource Management (SIM). SIM

often refers particularly to software used to manage storage networks and deices. By

contrast! the term Cstorage managementC can refer to deices and processes! as well as actual

software. 5n addition! SIM usually refers specifically to software for allocating storage

capacity based on company policies and ongoing eents. 5t may include asset management!

charge back! capacity management! configuration management! data and media migration!

eent management! performance and aailability management! policy management! quota

management! and media management capabilities. 5n short! SIM is a subset of storage

managementL howeer! the two terms are sometimes used interchangeably.

+rocessor management in windows

The heart of managing the processor comes down to two related issues#

• 6nsuring that each process and application receies enough of the processor=s time to

function properly

•

/sing as many processor cycles as possible for real work 

The basic unit of software that the operating system deals with in scheduling the work done

 by the processor  is either a process or a tread! depending on the operating system.

5t=s tempting to think of a process as an application! but that gies an incomplete picture of 

how processes relate to the operating system and hardware. The application you see (word

 processor! spreadsheet or game) is! indeed! a process! but that application may cause seeral

other processes to begin! for tasks like communications with other deices or other 

computers. There are also numerous processes that run without giing you direct eidence

that they eer e*ist. 9or e*ample! Eindows <2 and /D5< can hae do4ens of background

 processes running to handle the network! memory management! disk anagement!irus checks

and so on.

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Task . "dentify and describe te arcitecture of selected multi-user %& weter it is

monolitic, micro-kernel, layered, modular, or a ybrid.

Solution#-inu* is one of popular ersion of /D5< operating System. 5t is open source as its

source code is freely aailable. 5t is free to use. inu* was designed considering /D5<

compatibility. 5t=s functionality list is quite similar to that of /D5<.

)rcitecture %f linux

inu* System "rchitecture is consists of following layers

• ardware layer - 0ardware consists of all peripheral deices (I"M, 0, 2/

etc).

• 4ernel  - ore component of Operating System! interacts directly with hardware!

 proides low leel serices to upper layer components.

• &ell - "n interface to kernel! hiding comple*ity of kernel=s functions from users.

Takes commands from user and e*ecutes kernel=s functions.

• tilities  - /tility programs giing user most of the functionalities of an operating

systems.

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inu* is a a monolithic kernel where all serices (file system! 9S! deice driers!

etc) as well as core functionality (scheduling! memory allocation! etc.) are a tight knit

group sharing the same space. This directly opposes a microkernel . " microkernel

 prefers an approach where core functionality is isolated from system serices and

deice driers (which are basically 1ust system serices). 9or instance! 9S (irtual

file system) and block deice file systems (i.e. mini*fs) are separate processes that run

outside of the kernel=s space! using 52 to communicate with the kernel! other 

serices and user processes. 5n short! if it=s amodule  in inu*! it=s a service in a

microkernel! indicating an isolated process.

)rcitecture of Windows(-

ardware )bstraction Layer#-The hardware abstraction layer (0") is located directly

aboe the hardware on which E5DOES operates. 0" actually represents a software

module deeloped by hardware manufacturers that is bundled into E5DOES to allow it to

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operate on a specific hardware platform! such as 5ntel <N! 6 "lpha! or 5BM 2ower2.

0" hides the specifics of the hardware platform from the rest of the operating system and

represents the lowest leel of E5DOES. Thus! 0" proides true hardware platform

independence for the operating system. /sing 0"! software deelopers can create new

software without a lot of knowledge about the hardware platform. This allows software

deelopers to proide enhanced performance capabilities! such as additional deice dries.

0ardware endors can proide the interface between the operating system and the specific

hardware. ?ernel The kernel represents the core of the E5DOES operating system. "ll

operating systems hae a kernel. The key difference between the E5DOES kernel and

those found in other operating systems is the tasks managed. 2reious screen The

E5DOES kernel manages thread dispatching. (" threadP is a basic item that can be

scheduled by the kernel.) The kernel is also responsible for scheduling and processor 

synchroni4ation when the hardware platform has multiple processors. To perform scheduling!

the E5DOES kernel attempts to dispatch threads for e*ecution in a way that promotes the

most efficient use of the processors in the hardware platform. The actual dispatching of 

threads is based on their priority! with E5DOES supporting 87 priority leels to ma*imi4e

 processor use. The kernel always resides in real memory within the hardware platform=s

I"M and is nonpayable to disk. Ehen DT controls a multiprocessor platform! the kernel will

run on all processors at the same time and communicate with each other to goern the

distribution of threads. The DT 6*ecutie The DT 6*ecutie can be considered a common

serice proider because it is responsible for proiding a set of serices to all other operating

system components. The E5DOES 6*ecutie is the highest leel within the kernel mode

of the operating system. "s indicated in 6*hibit %! the 6*ecutie consists of si* core modules

that proide an interface between users and computers (represented by irtual OS Machines

and 6nironment Subsystems) and the kernel. irtual OS Machines support OS or %N-bit

Eindows 8.< applications. E5DOES proides support by creating irtual machines and

then implementing the required enironment within such a machine! resulting in the term

irtual OS machines.P 5n comparison! enironment subsystemsP are enironments that

may be required to operate on top of E5DOES. 6*amples of currently supported

enironment subsystems include OS,7! 2OS5<! and Ein87 (the E5DOES subsystem).

Ob1ect Manager The ob1ect manager names! retains! and proides security for ob1ects used by

the operating system. 5n a E5DOES enironment! an ob1ect represents physical items as

well as the occurrence of defined situations. Thus! an ob1ect can represent directories! files!

 physical hardware ports! semaphores! eents! and threads. "n ob1ect-oriented approach is

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used to manage ob1ects. 5f network managers are using E5DOES! they can iew the status

of eent ob1ects through the DT 6ent iewer! which is proided in the operating system as

an administratie tool. 2rocess Manager 5n a E5DOES enironment! a process represents

an address space! a group of ob1ects defined as a resource! or a set of threads. Thus! each of 

these entities is managed by the process manager. 5n doing so! the process manager combines

those entities into a irtual machine!P on which a program e*ecutes. 0ere the term irtual

machineP represents a set of resources required to proide support for the e*ecution of a

 program. E5DOES permits multiple irtual machines to be established! allowing

multiprocessing capability. irtual Memory Manager E5DOES uses a special file on the

hardware platform=s hard disk for additional memory beyond aailable I"M. That file is

referred to as a irtual memory paging or swap file and is automatically created when the

operating system is installed. 2reious screen The irtual Memory Manager manages the use

of irtual memory as a supplement to physical I"M. 9or e*ample! when one program cannot

completely fit into I"M because of its si4e or the current occupancy by other e*ecuting

 programs! the irtual Memory Manager might swap one program currently in memory to

disk to enable another program to e*ecute! or it could swap portions of the program

requesting e*ecution between I"M and the hard disk to e*ecute portions of the program in a

 predefined sequence. "lthough the operation of the irtual Memory Manager is transparent to

 programs using it! network managers can change the paging file si4e. To do so! they would

first select the System icon in the ontrol 2anel and then select the irtual Memory entry

from the resulting display. This action results in the display of a dialog bo* labeled irtual

Memory. 6*hibit 7 illustrates the irtual Memory dialog bo* with its default settings shown

for a 2entium processor.

"0% $anager(- The 5nput,Output (5,O) Manager is responsible for managing all input and

output to and from storage and the network. To perform its required functions! the 5,O

Manager uses four other lower-leel subsystemsQthe ache Manager! file system driers!

hardware deice driers! and network driers. The ache Manager proides a dynamic cache

space in I"M that increases and decreases based on aailable memory. 9ile system driers

 proide support for two file systems! the file allocation table (9"T) and the high performance

file system (029S). The 9"T file system proides backward support for OS and %N-bit

Eindows 8.<-based programs! whereas the 029S enables support of the new file system for 

E5DOES 87- bit applications.

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" ybrid kernel is an operating system kernel architecture that attempts to combine aspects

and benefits of  microkernel and monolithic kernel architectures used in computeroperating

systems. The traditional kernel categories are monolithic

kernels and microkernels (with nanokernels and e*okernels seen as more e*treme ersions of 

microkernels). The ChybridC category is controersial! due to the similarity of hybrid kernels

and ordinary monolithic kernelsL the term has been dismissed by inus Toralds as simple

marketing

One prominent e*ample of a hybrid kernel is the Microsoft  DT kernel that powers all

operating systems in the E5DOES family! up to and including Eindows %& and Eindows

Serer 7&%7! and powers Eindows 2hone ! Eindows 2hone .%! and <bo* One. DT-based

Eindows is classified as a hybrid kernel (or a macrokernel F7G) rather than a monolithic kernel

 because the emulation subsystems run in user-mode serer processes! rather than in kernel

mode as on a monolithic kernel! and further because of the large number of design goals

which resemble design goals of Mach (in particular the separation of OS personalities from a

general kernel design). onersely! the reason DT is not a microkernel system is because

most of the system components run in the same address space as the kernel! as would be the

case with a monolithic design (in a traditional monolithic design! there would not be a

microkernel per se! but the kernel would implement broadly similar functionality to DT=s

microkernel and kernel-mode subsystems).

The adantage to a microkernel is that any failed serice can be easily restarted! for instance!

there is no kernel halt if the root file system throws an abort.

Task . 3xplain te concept of paging as used in memory management by multiuser

operating systems. *ompare and contrast te implementations of paging in selected

$ulti-user %&.

SO/T5OD#-5n computer  operating systems! paging is one of the memory

management schemes by which a computer stores and retriees data from the secondary

storage for use in main memory.F%G 5n the paging memory-management scheme! the operating

system retriees data from secondary storage in same-si4e  blocks called pages. The main

adantage of paging oer memory segmentation is that it allows the physical address space of 

a process to be non contiguous. Before paging came into use! systems had to fit whole

 programs or their whole segments into storage contiguously!   which caused

arious storage and fragmentation problems.

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2aging is an important part of irtual memory implementation in most contemporary general-

 purpose operating systems! allowing them to use secondary storageFaG for data that does not fit

into physical random-access memory (I"M).

Linux +aging(- One basic concept in the inu* implementation of irtual memory is the

concept of a page. " page is a :?b area of memory and is the basic unit of memory with

which both the kernel and the 2/ deal. "lthough both can access indiidual bytes (or een

 bits)! the amount of memory that is managed is usually in pages.

5f you are reading a book! you do not need to hae all the pages spread out on a table for you

to work effectiely 1ust the page you are currently using. 5 remember many times in collegewhen 5 had the entire table top coered with open books! including my notebook. "s 5 was

studying! 5 would read a little from one book! take notes on what 5 read! and! if 5 needed more

details on that sub1ect! 5 would either go to a different page or a completely different book.

irtual memory in inu* is ery much like that. Rust as 5 only need to hae open the pages 5

am working with currently! a process needs to hae only those pages in memory with which it

is working. ike me! if the process needs a page that is not currently aailable (not in

 physical memory)! it needs to go get it (usually from the hard disk).

Windows +aging #- Ehen a process is created! it can in principle make use of the entire user 

space of 7 Abytes (minus %7 ?bytes). This space is diided into fi*ed-si4e pages! any of 

which can be brought into main memory. 5n practice! to simplify the accounting! a page can

 be in one of three states# "ailable# 2ages not currently used by this process. Iesered# "

set of contiguous pages that the irtual memory manager sets aside for a process but does not

count against the process=s memory quota until used. Ehen a process needs to write to

memory! some of the resered memory is committed to the process. ommitted# 2ages for 

which the irtual memory manager has set aside space in its paging file (e.g.! the disk file to

which it writes pages when remoing them from main memory). The distinction between

resered and committed memory is useful because it (%) minimi4es the amount of disk space

set aside for a particular process! keeping that disk space free for other processesL and (7)

enables a thread or process to declare an amount of memory that can be quickly allocated as

needed. The resident set management scheme used by Eindows is ariable allocation! local

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scope (see Table .:). Ehen a process is first actiated! it is assigned a certain number of 

 page frames of main memory as its working set. Ehen a process references a page not in

memory! one of the resident pages of that process is swapped out and the new page is brought

in. Eorking sets of actie processes are ad1usted using the following general conentions#

Ehen main memory is plentiful! the irtual memory manager allows the resident sets of 

actie processes to grow. To do this! when a page fault occurs! a new page is brought into

memory but no older page is swapped out! resulting in an increase of the resident set of that

 process by one page. -8%- Ehen memory becomes scarce! the irtual memory manager 

recoers memory for the system by moing less recently used pages out of the working sets

of actie processes! reducing the si4e of those resident sets.

Task Define and describe virtuali5ation. )lso discuss benefits and limitations of using

virtuali5ation.

Solution#- irtuali4ation is a combination of software and hardware engineering that creates

irtual Machines (Ms) - an abstraction of the computer hardware that allows a single

machine to act as if it where many machines.

• Eithout Ms# " single OS owns all hardware resources

• Eith Ms# Multiple OSes! each running its own irtual machine! share hardware

resources

• irtuali4ation enables multiple operating systems to run on the same physical

 platform

)dvantages of sing 6irtuali5ation(-

&erver *onsolidation(-  5t is not unusual to achiee irtual to physical machine

consolidation. This means that ten serer applications can be run on a single machine that had

required as many physical computers to proide the unique operating system and technical

specification enironments in order to operate. Serer utili4ation is optimi4ed and legacy

software can maintain old OS configurations while new applications are running in Ms with

updated platforms. "lthough a serer supporting many Ms will probably hae more

memory! 2/s! and other hardware it will use little or no more power and occupy the same

 physical space reducing utilities costs and real estate e*penditures.

Testing and development (-/se of a M enables rapid deployment by isolating the

application in a known and controlled enironment. /nknown factors such as mi*ed libraries

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caused by numerous installs can be eliminated. Seere crashes that required hours of 

reinstallation now take moments by simply copying a irtual image.

Dynamic Load 7alancing and Disaster 2ecovery(- "s serer workloads ary! irtuali4ation

 proides the ability for irtual machines that are oer utili4ing the resources of a serer to be

moed to underutili4ed serers. This dynamic load balancing creates efficient utili4ation of 

serer resources.

isaster recoery is a critical component for 5T! as system crashes can create huge economic

losses. irtuali4ation technology enables a irtual image on a machine to be instantly re-

imaged on another serer if a machine failure occurs.

6irtual Desktops (- Multinational fle*ibility proides seamless transitions between different

operating systems on a single machine reducing desktop footprint and hardware e*penditure.

"mproved &ystem 2eliability and &ecurity(-irtuali4ation of systems helps preent system

crashes due to memory corruption caused by software like deice driers. T-d for irected

5,O "rchitecture proides methods to better control system deices by defining the

architecture for M" and interrupt remapping to ensure improed isolation of 5,O resources

for greater reliability! security! and aailability.

LIIT!TI"N# "$ %I&TU!LIZ!TI"N

"n' major (o)n*i(' that you n''( to +' a)ar' o, +',or' you o-t ,or

virtuali.ation involv'* th' variou* limitation* that '/i*t Not all *'rv'r* ar'

a--liation* ar' *-'ially ('*ign'( to +' virtuali.ation3,ri'n(ly Thi* m'an*

that *om' a*-'t* o, your om-ut'r t'hnology )ithin your +u*in'** might not

l'av' you )ith th' availa+l' o-tion o, virtuali.ation

"nstant )ccess to Data(-

Since data is essential to your business it is essential that you only choose irtuali4ation

options that offer adequate data protection. Dot owning your own serers can put your data at

risk and this is not ideal. @ou do not want your data to be ulnerable.

Task . Discuss different levels or areas of virtuali5ation.

1. ardware 6irtuali5ation. &erver 6irtuali5ation

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. !etwork 6irtuali5ation

/. Desktop 6irtuali5ation

8. &torage virtuali5ation

Solution 8.7

ardware virtuali5ation  #-0ardware irtuali4ation is the abstraction of computing

resources from the software that uses those resources.

0ardware irtuali4ation installs a hyperisor  or irtual machine manager (MM)! which

creates an abstraction layer between the software and the underlying hardware. Once a

hyperisor is in place! software relies upon irtual representations of the computing

components such as irtual processors (2/s) rather than physical processors. 2opular hyperisors include Mware=s Sphere (6S<i) and Microsoft=s 0yper-.

irtuali4ed computing resources are proisioned into isolated instances called irtual

machines (Ms) where operating systems and applications can be installed. irtuali4ed

systems can host multiple Ms simultaneously! but eery M is logically isolated from eery

other M. This means a malware attack or crash of one M will not affect the other Ms.

Support for multiple Ms astly increase the system=s utili4ation and efficiency. 9or e*ample!

rather than buying %& separate serers to host %& physical applications! a single irtuali4ed

serer could potentially host those same %& applications installed into %& Ms on the same

system. This improed hardware utili4ation is a ma1or benefit of irtuali4ation and supports

enormous potential for system consolidation -- reducing the number of serers and power use

in enterprise data centers.

&erver virtuali5ation #-Serer irtuali4ation is the masking of serer resources (including the

number and identity of indiidual physical serers! processors! and operating systems) from

serer users. The intention is to spare the user from haing to understand and manage

complicated details of serer resources while increasing resource sharing and utili4ation and

maintaining the capacity to e*pand later.

!etwork virtuali5ation  #-Detwork irtuali4ation is a method of combining the aailable

resources in a network by splitting up the aailable bandwidth into channels! each of which is

independent from the others! and each of which can be assigned (or reassigned) to a particular 

serer or deice in real time. The idea is that irtuali4ation disguises the true comple*ity of 

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the network by separating it into manageable parts! much like your partitioned hard drie

makes it easier to manage your files.

Desktop 6irtuali5ation #-esktop irtuali4ation  remoes the need for a 2/ at each

computer station. 6ach user will still hae a monitor and mouse! but will hae their desktop

2/ irtually stored on a local serer. Benefits of desktop irtuali4ation include#

• irtual esktops can run on multiple types of hardware such as# workstations! Thin

lients! laptops and some smart phones.

• entrali4ing the irtuali4ed 2/sP of desktops proides increased stability through

 better administration of workstations and increased security because the host system

keeps all workstations up to date with patches and hot fi*es.

• irtual esktops can be quickly created after an initial originalP irtual machine has

 been producedQanytime a new desktop computer is needed! copy the original! gie it

a name and it is ready for immediate use.

&torage virtuali5ation  is the pooling of physical storage from multiple network storage

deices into what appears to be a single storage deice that is managed from a central

console. Storage irtuali4ation is commonly used in storage area networks (S"Ds).