File and Disk Maintenance

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Chapter 11

• File and Disk Maintenance

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File Systems

• A file system defines the structure and the rules
  used to read, write, and maintain information
  stored on a disk. (page 238)
• Which system used is determined by
• Hardware
• Software
• Security needs
• Need for a dual-booting system

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File Systems

• FAT 16 (file allocation table where the OS
  records how the disk space is used) oldest,
  created for DOS, supported by most OSs, cannot
  be installed on partitions larger than 2 GB, or
  on hard drives larger than 4GB.
• FAT 32 supports disks from 512 to 2TB,
  compatible with Windows 98 and up
• NTFS (new technology file system) better file
  security (Encrypting File System), disk
  compression, logging features, reliability and
  stability. NTFS volumes can not be accessed by
  DOS, or Windows 95 or Windows 98.

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File Systems

• Windows XP Professional keeps track of data by
  placing it into a file.
• To store and retrieve files
• Disk divided into tracks
• Tracks are divided into sectors
• Sectors grouped into clusters
• Number of sectors in a cluster is determined by
• Size of the hard drive
• File allocation system FAT, FAT32, NTFS, etc.

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• When you format a disk the operating systems
  creates concentric recording bands, called
  tracks, around the circumference of the disk.
  Then, the formatting program (in our case Windows
  XP) subdivides each track into equal parts,
  called sectors. Although not all of them are
  shown in this diagram, there are 80 concentric
  tracks on a 3 ½ inch high density diskette and
  each track is divided into 18 sectors. Each
  sector in turn contains 512 bytes.
• So lets see . . . . . 80 tracks X 18 sectors X
  2 sides X 512 bytes 1,474,560 bytes 1.4 MB

Tracks
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A hard disk has extremely smooth metal or glass
plates called platters (vs. the floppy mylar
disk of a floppy disk). Each platter is divided
into tracks and sectors by the format operation,
like a floppy disk, however the number of tracks
and sectors is different. The number of tracks
on a hard disk depends on the disk size and the
manufacturer.
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• A cluster, also known as an allocation unit,
  consists of one or more sectors of storage space,
  and represents the minimum amount of space that
  an operating system allocates when saving the
  contents of a file to a disk.
• The number of sectors per cluster is dependent on
  
• Type of disk (floppy disk, hard disk)
• Version of operating systems
• Size of disk
• Every sector contains 512 bytes. (NTFS does allow
  you to change this number.)
• The number of clusters per disk is determined by
  the filing system (FAT 16, FAT 32 or NTFS).

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• So, what does this all mean to us, as Windows XP
  users? The bigger your disk the bigger your
  clusters (because there is a maximum number of
  clusters per disk).
• Windows XP uses NTFS, so if your computer has
  more than a 32 GB hard drive and you save a 10 KB
  file then the system will use 64KB to save the
  file. Meaning that 54KB will be slack space.
• One way to help alleviate the problem of slack
  space is to partition the hard drive into smaller
  drives. Reducing the drive size will reduce
  the cluster size.

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What can cause a hard drive problem?

• Physical hard drive problems
• Wear and tear on hard disk
• Minimize with Power Management and/or Hibernation
• Head crash
• Minimize by placing system where it will not get
  knocked around.
• Software-related problems
• Viruses
• Minimize by using virus protection software

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Other potential problems

• Some error causing conditions to data that may be
  repairable
• Power surges
• Power outages
• Locked system
• not exiting a program correctly

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Detecting/Repairing Disk Errors with Check Disk

• The Check Disk utility is a disk analysis and
  repair utility that examines disks for errors
  and, where possible, repairs errors.
• Checks the logical structure
• Checks the physical integrity of the disks
  surface, if it finds a bad sector it will attempt
  to move the data to another location.
• Take care of Lost Clusters, Cross-linked clusters

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Detecting/Repairing Disk Errors with Check Disk

• Lost Clusters
• Have no directory entry in FAT
• Do not belong to any file
• Take up disk space -
• Unavailable for new data
• Cannot be retrieved/deleted
• Reasons for Lost Clusters
• Not exiting program properly
• Power surge/failure

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Detecting/Repairing Disk Errors with Check Disk

• FAT and directory table work in conjunction.
• Pointers, chain together all clusters that make
  up an individual file, give directions to the
  next cluster.

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Figure 11.1 Lost Clusters p. 540
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• Cross-Linked Files
• Two or more files claim same cluster as part of
  their chain
• One file claims same cluster twice
• Data in cross-linked cluster
• Usually correct for only one file
• May not be correct for any file

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Figure 11.2 Cross-Linked Files p. 540
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Detecting/Repairing Disk Errors with Check Disk

• Check Disk
• Can fix lost clusters automatically
  
• or
• Save them to disk as files

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Detecting/Repairing Disk Errors with Check Disk

• Check Disk
• CAN check/repair local hard drives, floppy disks,
  and removable drives
• CANNOT find/fix errors on CD-ROMs or network
  drives

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Detecting/Repairing Disk Errors with Check Disk

• Check Disk
• Should be used on a regular basis
• The first time you use it you should back up your
  disk before running check disk.
• Close all open programs when using this program,
  including screen saver
• If disk is formatted at NTFS, Windows XP
  Professional will automatically (without running
  Check Disk)
• Log all file transactions
• Replace bad clusters
• Store copies of key information for all files on
  NTFS volume

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Cleaning Up Your Disk

• Computer performance depends a great deal on the
  hard drive.
• Need disk space for
• New files
• Temporary files
• Documents waiting to be printed
• Cache files
• Cache storage area for often used information
  that can be accessed quickly
• Recycle

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Cleaning Up Your Disk

• Disk cleanup is a utility that helps maintain the
  hard disk.
• Intended for hard drives.
• Will remove the following
• Internet cache files
• Downloaded program files
• Offline web pages
• Offline lines, temporary offline files
• Temporary files
• Files in the recycle bin
• Windows components that you no longer use
• Installed programs that you no longer use
• Catalog files for the Content Indexer

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Contiguous and the Problem of Noncontiguous Files

• When a file is deleted
• Only entries in FAT deleted
• Space file occupied becomes available

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Contiguous and Noncontiguous Files

• Files are
• Contiguous written to adjacent clusters on a
  disk
• Noncontiguous (fragmented) written to a disk
  in nonadjacent clusters.
• So a Fragmented Disk has noncontiguous files. It
  takes longer to read a Fragmented Disk because
  the head must move around so much going to the
  various locations of the file clusters.

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Defragment the Disk to improve performance

• The defragger/disk optimization program
• Rearranges the files on a disk so that all parts
  of each files are store in consecutive clusters.
• It also records the clusters for one file right
  after the clusters for another file, and in the
  process, removes free space between files that
  would result in more fragmentation.
• At the end of defragmentation all the unused
  space is near the inner edge of the disk.

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Optimizing the Performance of Disks

• Prior to running Disk Defragmenter
• Run Check Disk and Disk Cleanup
• Remove all lost/cross-linked clusters and
  unnecessary files
• Close All open programs
• Allow ample time
• Back up disk

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Starting Programs Automatically

• Task Scheduler can be used
• to schedule any program
• to run at any time.

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Starting Programs Automatically

• When scheduling tasks to run unsupervised, be
  sure task . . .
• does not need user input.
• can exit when task is completed.

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Backing Up Your Data

• Backup - make a duplicate of file/s on one disk
  by copying to another medium.
• Retrieve files by restoring them.
• How do you lose data?
• User error
• Hardware failures
• Software problems
• Damage from hackers
• Damage from viruses
• Theft or vandalism
• Natural disaster

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Why backup?

• In 1994 Microsoft estimated it would take an
  average of 2000 hours to replace lost files on a
  typical hard disk (340-540 MB).
• Todays hard disks store gigabytes of data.
• TIME TO REPLACE LOST DATA COULD BE SUBSTANIAL!

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Approaches for Backing up Files

• Backing up files on a removable storage device.
• Write protect the backup.
• CD-R, Zip and JAZ
• Copying Files from a hard disk
• Useful when making a quick backup
• Using a backup utility
• Large set of files
• Can use variety of media floppy disks,
  removable disks or tapes, network drives, other
  hard disks
• Must use the restore feature

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Backup Media

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Backup Media cont.
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Backing Up Your Data

• Windows XP Professional supports five methods
  of backup
• Normal (Full) Backup every file
• Incremental Backup only files that have changed
  since the last normal or incremental backup
• Differential Backup selected files that have
  changed since the last time an all selected files
  backup was used.
• Daily Backup modified files only on day back up
  performed
• Copy Backup selected files

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Backing Up Your Data

• Full backup
• Longer to backup
• Faster to restore
• Incremental backup
• Faster to backup
• Slower to restore
• Usually use a combination.

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Backing Up Your Data

• Need a regular backup schedule.
• Wise to have more than one copy of backup media.
• Take care of the backup media.

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Backing Up Your Data

• Uses of Backup
• Archive data
• Make room on hard disk
• Transfer files to other computers
• Make new computer look like old system

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Restore

• Backup/Restore Wizard
• Backup option.
• Used to copy some/all files to original disk,
  another disk, or another directory.

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Automated System Recovery

• Automated System Recovery (ASR)
• Part of a built-in repair system for
• solving system problems (such as a
• boot problem or registry problem)
• Not a substitute for backing up data
• Does not save program files or any data files.
• A snapshot of your system files.

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The Registry

• Configuration information
• Contains data about the system
• Hardware
• Applications
• User preferences
• Previous Windows versions used .INI files for
  configuration information.

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The Registry

• Today, Windows XP Professional uses single
  location, the Registry, for hardware, system
  software, and application configuration
  information.

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The Registry

• Registry information comes from
• Installation of Windows XP Professional
• Booting of Windows XP Professional
• Applications
• System and User interaction

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The Registry

• Registry
• Critical to the operation of Windows XP
  Professional.

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The Registry

• The Registry can be restored by using
• Recovery Console
• Last Known Good Configuration
• Safe Mode
• Loads minimum amount of drivers and
  functionality that allows Windows to run

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System Restore

• System Restore can
• Undo changes made to computer
• Roll back computer to more stable state
• Save email messages, browsing history, etc.
• Use calendar to select which date you want to
  restore to
• Provide several restore points

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System Restore

• System restore does not save or restore
  documents.
• All system restores are reversible

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Plug and Play and Device Drivers

• Plug and Play automates adding new hardware to
  computer.
• For Plug and Play to work
• Computer needs Plug and Play compatible BIOS
• Device to be installed is Plug and Play
  compatible
• Compatible Plug and Play Operating System

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The Paging File

• Computers system performance impacted by
• Processor
• Amount of physical memory
• Paging file
• Space on the hard drive used as virtual memory
  when the system runs out of physical memory

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The Paging File

• Paging file
• Slows down performance
• Enlarges operating space
• User can set place/size of paging file.
• BUT
• Microsoft recommends letting Windows manage
  paging file.

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Administrative Tools and System Information

• System Information
• Collects/displays system configuration
  information for local and remote computers
• Microsoft Management Console (MMC)
• Tool used to create, save, and open
  collections of administrative tools