Chapter 11 - System Management

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Chapter 11 - System Management
CIS106 Microcomputer Operating Systems Gina
Rue CIS Faculty
Ivy Tech State College Northwest Region 01
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Introduction - System Management

• Four parts of the OS
• Memory Manager
• Processor Manager
• Device Manager
• File Manager
• Each part of the OS depends on the other parts

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Introduction - System Management

• OS parts work together
• System designer has to consider trade-offs to
  improve the systems efficiency
• improve performance of one component
• cost of that improvement
• how it might affect the performance of the
  remainder of the system
• Some methods are used to monitor measure system
  performance, accounting security

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Evaluating an OS

• Every OS is different
• Most were originally designed to work with
  certain hardware or category of computer, and to
  meet specific goals of the users
• computing environments, multiple systems
• casual users, programmers
• response time, throughput

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Evaluating an OS

• To evaluate an OS, we need to understand
• design goals
• history
• how it communicates with users
• how resources are managed
• what trade-offs were made to achieve goals
• Need to balance its strengths against its
  weaknesses

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OS Four Components

• Improvements in a system can only be made after
  extensive analysis of the needs of the systems
  managers users
• Making one change, you may be trading one set of
  problems for another
• Key to consider the performance of the entire
  system and not just individual components

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OS Four Components

• Memory Management
• if you increase memory or change another memory
  allocation scheme, you must consider the actual
  operating environment
• there is a trade-off between memory use and CPU
  overhead
• as memory management algorithms grow more
  complex, the CPU overhead increases and overall
  performance can suffer

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OS Four Components

• Processor Management
• Lets say you decide to implement a
  multiprogramming system to increase your
  processors utilization
• multiprogramming requires a great deal of
  synchronization between the memory and processor
  managers and I/O devices
• The trade-off better use of the CPU vs.
  increased overhead, slower response time,
  decreased throughput

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OS Four Components

• Device Management
• Several ways to improve I/O device utilization
• Blocking reduces the number of physical I/O
  requests
• Buffering helps the CPU match the slower speed of
  I/O devices
• Rescheduling I/O requests can help optimize I/O
  times
• These are trade-offs each of these options also
  increases CPU overhead and uses additional memory
  space

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OS Four Components

• File Management
• looks at how secondary storage allocation schemes
  help the user organize and access files on the
  system
• affects overall system performance
• closely related to the device on which the files
  are stored
• different schemes offer different flexibility,
  but trade-off for increased file flexibility is
  increased CPU overhead

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Measuring System Performance

• Total System Performance - the efficiency with
  which a computer system meets its goals - how
  well it serves it users
• A systems efficiency is affected by 3 major
  components
• the users programs
• operating system programs
• hardware units

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Measuring System Performance

• Measurement Tools
• throughput
• capacity
• response time
• turnaround time
• resource utilization
• availability MTBF MTTR
• reliability

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Measuring System Performance

• Feedback loops
• to prevent the processor from spending more time
  doing overhead then executing jobs, the OS must
  continuously monitor the system and feed this
  information to the Job Scheduler
• negative feedback loop
• when system becomes too congested, signals the
  appropriate manager to slow down the arrival of
  the processes
• positive feedback loop
• when the system becomes underutilized, causes the
  arrival rate to increase

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Measuring System Performance

• Monitoring
• System measurements must include hardware units,
  OS, compilers, and other system software
• Benchmarks are used to objectively measure and
  evaluate a systems performance by running a set
  of jobs representative of work normally done by
  the system
• Benchmarks are useful when comparing systems that
  gone through extensive changes or by vendors to
  demonstrate advantages of new system components

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Accounting

• Accounting functions - pay the bills and keeps
  the system financially operable
• Multi-user environment, the OS must be able to
• set up user accounts
• assign passwords
• identify resources available to each user
• define quotas for available resources

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Accounting

• Pricing policies measurements
• total amount of time
• CPU time
• main memory usage
• secondary storage used during program execution
  or during billing period
• use of system software
• number of I/O operations time spent waiting for
  I/O completion
• Number of input records read, number of output
  records printed
• number of page faults

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Accounting

• Maintaining billing records on-line
• Advantage
• status of each user can be checked before the
  users job is allowed to enter the READY queue
• Disadvantage
• overhead, an accounting program is kept active,
  memory space is used and CPU processing is
  increased
• one compromise is to defer the accounting program
  until off-hours

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Ethics

• Cannot be ignored by users or system
  administrators
• Organizations should have published policies
  clearly stating which actions will or will not be
  condoned
• individual needs for privacy
• organizations need to protect proprietary
  information
• publics right to know as illustrated in freedom
  of information laws

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Ethics

• Ethical lapses by authorized or unauthorized
  users can have severe consequences
• illegally copied software
• plagiarism
• eavesdropping on email
• hacking
• unethical use of technology

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System Security

• The system has conflicting needs
• to share resources
• to protect resources
• With the advent of data communication,
  networking, modern telecommunications software,
  computer security has become much more difficult

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System Security

• System Vulnerabilities
• accidental incomplete modification of data
• data values are incorrectly encoded
• intentional unauthorized access
• wire tapping
• repeated trials
• trash collection
• trap doors

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System Security

• System Assaults Computer Viruses
• A virus is any unauthorized program that is
  designed to
• gain access to a computer system
• lodge itself in a secretive way by incorporating
  itself into other legitimate programs
• replace itself
• viruses need other programs to spread
• worm
• Trojan horse
• logic bomb
• pirated software

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System Security

• System Assaults Computer Viruses
• Software to combat viruses can be purchased to
  protect against viruses
• most extreme protection for sensitive data is
  encryption
• putting data into secret code
• disadvantages to encryption
• increase the systems overhead
• the system becomes totally dependent on the
  encryption process itself

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System Security

• Managing Systems
• most systems use a combination of several
  protection devices
• passwords
• backups
• maintenance of written security policies
• training users in proper data management

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Summary

• OS is the orchestrated cooperation of every piece
  of hardware and software
• Trade-offs must be made for optimal performance
• Appropriate measurement tools and techniques are
  used to verify effectiveness of the system before
  after modifications then evaluate degree of
  improvement

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Summary

• Important to keep system secure
• System is only as good as the integrity of the
  data thats stored on it
• Prevention is the best form of system security