Chapter 11 - Chapter 11 - System ManagementSystem Management

Ivy Tech State College Northwest Region 01

CIS106 Microcomputer Operating Systems

Gina RueCIS Faculty

See Illustration p.245 2

Introduction - Introduction - System ManagementSystem Management

• Four parts of the OSFour parts of the OS– Memory ManagerMemory Manager

– Processor ManagerProcessor Manager

– Device ManagerDevice Manager

– File ManagerFile Manager

• Each part of the OS depends on the Each part of the OS depends on the other partsother parts

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Introduction - System Introduction - System ManagementManagement

• OS parts work togetherOS parts work together

• System designer has to consider trade-offs to System designer has to consider trade-offs to improve the system’s efficiencyimprove the system’s efficiency– improve performance of one componentimprove performance of one component

– cost of that improvementcost of that improvement

– how it might affect the performance of the remainder how it might affect the performance of the remainder of the systemof the system

• Some methods are used to monitor & measure Some methods are used to monitor & measure system performance, accounting & securitysystem performance, accounting & security

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Evaluating an OSEvaluating an OS

• Every OS is differentEvery OS is different

• Most were originally designed to work Most were originally designed to work with certain hardware or category of with certain hardware or category of computer, and to meet specific goals of computer, and to meet specific goals of the usersthe users– computing environments, multiple systemscomputing environments, multiple systems

– casual users, programmerscasual users, programmers

– response time, throughputresponse time, throughput

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Evaluating an OSEvaluating an OS

• To evaluate an OS, we need to understandTo evaluate an OS, we need to understand– design goalsdesign goals

– historyhistory

– how it communicates with usershow it communicates with users

– how resources are managedhow resources are managed

– what trade-offs were made to achieve goalswhat trade-offs were made to achieve goals

• Need to balance its strengths against its Need to balance its strengths against its weaknessesweaknesses

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OS Four ComponentsOS Four Components

• Improvements in a system can only be Improvements in a system can only be made after extensive analysis of the needs made after extensive analysis of the needs of the system’s managers & usersof the system’s managers & users

• Making one change, you may be trading Making one change, you may be trading one set of problems for anotherone set of problems for another

• Key to consider the performance of the Key to consider the performance of the entire system and not just individual entire system and not just individual componentscomponents

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OS Four ComponentsOS Four Components

• Memory ManagementMemory Management– if you increase memory or change another if you increase memory or change another

memory allocation scheme, you must consider memory allocation scheme, you must consider the actual operating environment the actual operating environment

– there is a trade-off between memory use and there is a trade-off between memory use and CPU overheadCPU overhead

– as memory management algorithms grow as memory management algorithms grow more complex, the CPU overhead increases more complex, the CPU overhead increases and overall performance can sufferand overall performance can suffer

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OS Four ComponentsOS Four Components

• Processor ManagementProcessor Management– Let’s say you decide to implement a Let’s say you decide to implement a

multiprogramming system to increase your multiprogramming system to increase your processor’s utilizationprocessor’s utilization

– multiprogramming requires a great deal of multiprogramming requires a great deal of synchronization between the memory and synchronization between the memory and processor managers and I/O devicesprocessor managers and I/O devices

– The trade-off: better use of the CPU vs. increased The trade-off: better use of the CPU vs. increased overhead, slower response time, & decreased overhead, slower response time, & decreased throughputthroughput

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OS Four ComponentsOS Four Components• Device ManagementDevice Management

– Several ways to improve I/O device utilizationSeveral ways to improve I/O device utilization• Blocking reduces the number of physical I/O requestsBlocking reduces the number of physical I/O requests

• Buffering helps the CPU match the slower speed of Buffering helps the CPU match the slower speed of I/O devicesI/O devices

• Rescheduling I/O requests can help optimize I/O timesRescheduling I/O requests can help optimize I/O times

– These are trade-offs: each of these options These are trade-offs: each of these options also increases CPU overhead and uses also increases CPU overhead and uses additional memory spaceadditional memory space

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OS Four ComponentsOS Four Components

• File ManagementFile Management– looks at how secondary storage allocation schemes looks at how secondary storage allocation schemes

help the user organize and access files on the help the user organize and access files on the systemsystem

– affects overall system performanceaffects overall system performance

– closely related to the device on which the files are closely related to the device on which the files are storedstored

– different schemes offer different flexibility, but different schemes offer different flexibility, but trade-off for increased file flexibility is increased trade-off for increased file flexibility is increased CPU overheadCPU overhead

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Measuring System Measuring System PerformancePerformance

• Total System Performance - “Total System Performance - “the efficiency the efficiency with which a computer system meets its with which a computer system meets its goals” - how well it serves it usersgoals” - how well it serves it users

• A system’s efficiency is affected by 3 major A system’s efficiency is affected by 3 major components:components:– the user’s programsthe user’s programs

– operating system programsoperating system programs

– hardware unitshardware units

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Measuring System Measuring System PerformancePerformance

• Measurement ToolsMeasurement Tools– throughputthroughput

– capacitycapacity

– response timeresponse time

– turnaround timeturnaround time

– resource utilizationresource utilization

– availability: MTBF & MTTRavailability: MTBF & MTTR

– reliabilityreliability

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Measuring System Measuring System PerformancePerformance

• Feedback loopsFeedback loops– to prevent the processor from spending more time doing to prevent the processor from spending more time doing

overhead then executing jobs, the OS must continuously overhead then executing jobs, the OS must continuously monitor the system and feed this information to the Job monitor the system and feed this information to the Job SchedulerScheduler

– negative feedback loopnegative feedback loop

when system becomes too congested, signals the appropriate when system becomes too congested, signals the appropriate manager to slow down the arrival of the processesmanager to slow down the arrival of the processes

– positive feedback looppositive feedback loop

when the system becomes underutilized, causes the arrival when the system becomes underutilized, causes the arrival rate to increaserate to increase

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Measuring System Measuring System PerformancePerformance

• MonitoringMonitoring

– System measurements must include hardware units, System measurements must include hardware units, OS, compilers, and other system softwareOS, compilers, and other system software

– Benchmarks are used to objectively measure and Benchmarks are used to objectively measure and evaluate a system’s performance by running a set of evaluate a system’s performance by running a set of jobs representative of work normally done by the jobs representative of work normally done by the systemsystem

– Benchmarks are useful when comparing systems that Benchmarks are useful when comparing systems that gone through extensive changes or by vendors to gone through extensive changes or by vendors to demonstrate advantages of new system componentsdemonstrate advantages of new system components

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AccountingAccounting

• Accounting functions - pay the bills and Accounting functions - pay the bills and keeps the system financially operablekeeps the system financially operable

• Multi-user environment, the OS must be Multi-user environment, the OS must be able to:able to:– set up user accountsset up user accounts

– assign passwordsassign passwords

– identify resources available to each useridentify resources available to each user

– define quotas for available resourcesdefine quotas for available resources

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AccountingAccounting• Pricing policies measurementsPricing policies measurements

– total amount of timetotal amount of time

– CPU timeCPU time

– main memory usagemain memory usage

– secondary storage used during program execution or during secondary storage used during program execution or during billing periodbilling period

– use of system softwareuse of system software

– number of I/O operations & time spent waiting for I/O number of I/O operations & time spent waiting for I/O completioncompletion

– Number of input records read, number of output records printedNumber of input records read, number of output records printed

– number of page faultsnumber of page faults

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AccountingAccountingMaintaining billing records on-lineMaintaining billing records on-line

• AdvantageAdvantage– status of each user can be checked before the user’s status of each user can be checked before the user’s

job is allowed to enter the READY queuejob is allowed to enter the READY queue

• DisadvantageDisadvantage– overhead, an accounting program is kept active, overhead, an accounting program is kept active,

memory space is used and CPU processing is increasedmemory space is used and CPU processing is increased

– one compromise is to defer the accounting program one compromise is to defer the accounting program until off-hours until off-hours

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EthicsEthics

• Cannot be ignored by users or system Cannot be ignored by users or system administratorsadministrators

• Organizations should have published policies Organizations should have published policies clearly stating which actions will or will not be clearly stating which actions will or will not be condonedcondoned– individual needs for privacyindividual needs for privacy

– organization’s need to protect proprietary informationorganization’s need to protect proprietary information

– public’s right to know as illustrated in freedom of public’s right to know as illustrated in freedom of information lawsinformation laws

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EthicsEthics

• Ethical lapses by authorized or Ethical lapses by authorized or unauthorized users can have severe unauthorized users can have severe consequencesconsequences– illegally copied softwareillegally copied software

– plagiarismplagiarism

– eavesdropping on emaileavesdropping on email

– hackinghacking

– unethical use of technologyunethical use of technology

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System SecuritySystem Security

– The system has conflicting needs:The system has conflicting needs:• to share resourcesto share resources

• to protect resourcesto protect resources

– With the advent of data With the advent of data communication, networking, modern communication, networking, modern telecommunications software, telecommunications software, computer security has become much computer security has become much more difficultmore difficult

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System SecuritySystem Security– System VulnerabilitiesSystem Vulnerabilities

•accidental incomplete modification of dataaccidental incomplete modification of data

•data values are incorrectly encodeddata values are incorrectly encoded

• intentional unauthorized accessintentional unauthorized access

•wire tappingwire tapping

•repeated trialsrepeated trials

•trash collectiontrash collection

•trap doorstrap doors

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System SecuritySystem Security– System Assaults: Computer VirusesSystem Assaults: Computer Viruses

•A virus is any unauthorized program that is A virus is any unauthorized program that is designed to: designed to:

– gain access to a computer systemgain access to a computer system– lodge itself in a secretive way by incorporating itself lodge itself in a secretive way by incorporating itself

into other legitimate programsinto other legitimate programs– replace itselfreplace itself

•viruses need other programs to spreadviruses need other programs to spread– wormworm– Trojan horseTrojan horse– logic bomblogic bomb– ““pirated” softwarepirated” software

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System SecuritySystem Security– System Assaults: Computer VirusesSystem Assaults: Computer Viruses

•Software to combat viruses can be Software to combat viruses can be purchased to protect against virusespurchased to protect against viruses

•most extreme protection for sensitive most extreme protection for sensitive data is encryptiondata is encryption

– putting data into secret codeputting data into secret code

•disadvantages to encryptiondisadvantages to encryption– increase the system’s overheadincrease the system’s overhead– the system becomes totally dependent on the the system becomes totally dependent on the

encryption process itselfencryption process itself

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System SecuritySystem Security– Managing SystemsManaging Systems

•most systems use a combination most systems use a combination of several protection devicesof several protection devices

– passwordspasswords– backupsbackups– maintenance of written security maintenance of written security

policiespolicies– training users in proper data training users in proper data

managementmanagement

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SummarySummary

• OS is the orchestrated cooperation of every OS is the orchestrated cooperation of every piece of hardware and softwarepiece of hardware and software

• Trade-offs must be made for optimal Trade-offs must be made for optimal performanceperformance

• Appropriate measurement tools and Appropriate measurement tools and techniques are used to verify effectiveness techniques are used to verify effectiveness of the system before & after modifications of the system before & after modifications & then evaluate degree of improvement& then evaluate degree of improvement

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SummarySummary

• Important to keep system secureImportant to keep system secure

• System is only as good as the System is only as good as the integrity of the data that’s stored on integrity of the data that’s stored on itit

• Prevention is the best form of Prevention is the best form of system securitysystem security