Chapter Overview

1
Chapter Overview

• Backups
• Antivirus Policies
• Patches and Updates

2
What Is a Backup?

• Backups are copies of data that you make on a
  regular basis, allowing you to restore lost data
  in a timely manner.
• Even if you have other storage technologies in
  place that provide fault tolerance, you still
  need a backup solution.
• Networks both complicate and simplify the process
  of making regular backups.
• More complicated because you have data stored on
  multiple devices that must be protected
• Simpler because you can use the network to access
  those devices
• A network backup strategy specifies what data you
  back up, how often you back it up, and what
  medium you use to store the backups.
• The backup hardware, software, and administrative
  policies you will use depend on how much data you
  have to back up, how much time you have to back
  it up, and how much protection you want to
  provide.

3
Selecting a Backup Drive

• Try to automate as much of the backup process as
  possible.
• Select a device that can store all of your data
  without frequent media changes.
• Consider the speed at which the drive writes data
  to the medium.
• The amount of time that you have to perform your
  backups is sometimes called the backup window.
• The backup device that you choose should depend
  in part on
• The amount of data you have to protect
• The amount of time that you have to back it up

4
Determining Backup Costs

• Cost is always a factor in selecting a hardware
  product.
• Faster drives are generally more expensive.
• A low-end backup drive can cost 100 to 200,
  which is suitable for backing up a home computer
  where speed is not a major factor.
• High-end backup drives can have prices that run
  into five figures.
• When you evaluate backup devices, be aware of the
  products media costs as well.
• Some products might seem economical because the
  drive is inexpensive, but in the long run they
  might not be, because the media are so expensive.
• Determine the cost per megabyte of the storage a
  drive provides.
• Divide the price of the medium by the number of
  megabytes it can store, and use this figure to
  compare the relative cost of various devices.

5
Selecting a Drive Interface

• Backup devices can use any of the standard
  computer interfaces Integrated Drive Electronics
  (IDE), universal serial bus (USB), or Small
  Computer System Interface (SCSI).
• The most common interface used in high-end
  network backup solutions is SCSI.
• SCSI devices operate more independently than IDE
  devices, which means that the backup process is
  more efficient.
• SCSI devices can maintain a queue of commands
  that they have received from the host adapter and
  can execute them sequentially and independently.
• When multiple IDE devices share a channel, only
  one operates at a time.
• Magnetic tape drives require a consistent stream
  of data to write to the tape with maximum
  effectiveness.

6
A Typical Magnetic Tape Drive
7
Magnetic Tape Drives

• Magnetic tape drives are the most common hardware
  devices used to back up data.
• Tape drives are not random access devices.
• You cannot mount a tape drive in a computers
  file system, assign it a drive letter, and copy
  files to it, as you can with a hard disk drive.
• A special software program is required to address
  the drive and send the data you select to it for
  storage.
• Magnetic tape drives are well suited for backups,
  and they offer several advantages
• Fast
• Hold a lot of data
• Low media cost, often less than one-half cent per
  megabyte
• Tape drives are useless for anything other than
  backups.

8
Magnetic Tape Technologies
9
CD-ROM Drives

• Writable CD-ROM drives, such as compact
  disc-recordables (CD-Rs) and compact disc
  rewritables (CD-RWs), can be used as backup
  devices.
• Advantages
• The low cost of the media makes CDs an economical
  solution.
• Many computers already have CD-ROM drives, which
  eliminates the need to buy a dedicated backup
  drive.
• Disadvantages
• By backup device standards, the capacity of a CD
  is low, about 650 MB.
• For network backups, CD-ROMs are usually
  inadequate.
• Network backup software products usually do not
  recognize CD-R and CD-RW drives.

10
Cartridge Drives

• Removable cartridge drives, such as Iomegas Zip
  and Jaz drives, can be used for backups.
• Zip cartridges hold only 100 MB or 250 MB, which
  makes them less practical than CDs for backups.
• Jaz drives are available in 1-GB and 2-GB
  versions, which is sufficient for a backup
  device.
• Cartridge drives mount into a computers file
  system.
• You can assign a drive letter to a cartridge
  drive and copy files to it just as you can assign
  a drive letter and copy files to a hard drive.
• Disadvantage the cost of the media is extremely
  high, making cartridge drives impractical for
  network backups.

11
A Typical Autochanger
12
Autochangers

• An autochanger is a unit that contains one or
  more drives and a robotic mechanism that swaps
  the media in and out of the drives.
• Some autochangers are small devices with a single
  drive and an array that holds four or five tapes.
  
• Others are enormous devices with as many as four
  drives and an array of 100 tapes or more.
• When a backup job fills one tape (or other
  storage medium), the mechanism extracts it from
  the drive and inserts another, and the job
  continues.
• If you buy a large enough autochanger, you can
  create a long-term backup strategy that allows
  backups to run completely unattended for weeks at
  a time.
• Autochanger prices can be astonishingly high,
  reaching as much as six figures in some cases.

13
Target Selection

• The most basic function of a backup software
  program is to let you select what you want to
  back up, sometimes called the target.
• A good backup program enables you to select
  targets by selecting
• Entire computers
• Specific drives on those computers
• Specific directories on the drives
• Specific files in specific directories

14
The Backup Dialog Box in the Windows 2000 Backup
Program
15
Full, Incremental, and Differential Backups

• A full backup copies the entire contents of a
  computers drives to tape or another medium.
• When you perform a full backup every day, most of
  the files you are writing to the tape are exactly
  the same as they were the previous day.
• Between full backups, administrators perform
  special types of filtered jobs that back up only
  the recently modified files.
• An incremental job backs up only the files
  changed since the last backup job of any kind.
• A differential job backs up only the files that
  have changed since the last full backup.
• The backup software filters the files for backup
  jobs by using a special file attribute called the
  archive bit, which is on every file on the
  computer.

16
Archive Bits

• The archive bit for a file is activated by any
  application that modifies that file.
• When the backup program scans the target drive
  during an incremental or differential job, it
  selects for backup only the files with active
  archive bits.
• During a full backup, the software backs up the
  entire contents of a computers drives, and also
  resets the archive bit on all of the files.
• As work on the computer proceeds after the backup
  job is completed, files are modified, and the
  archive bits for the modified files are
  activated.
• The next day, you can run an incremental or
  differential backup job, which filters out all
  files that do not have an active archive bit.
• Compared to a full backup, an incremental or
  differential backup job is usually much smaller,
  so it takes less time and less tape.

17
Incremental Jobs

• Incremental jobs reset the archive bits on the
  files they back up.
• When you run an incremental job, you back up only
  the files that have changed since the last
  backup, whether it was a full backup or an
  incremental backup.
• If you restore an entire computer, you must first
  perform a restore from the last full backup tape,
  and then restore each incremental job performed
  since the last full backup.
• The order of the restore jobs is essential if you
  want the computer to have the latest version of
  every file.
• Advantage uses the least amount of tape
• Disadvantage lengthens the restore process

18
Differential Jobs

• Differential jobs do not reset the archive bit on
  the files they back up.
• Every differential job backs up all of the files
  that have changed since the last full backup.
• Advantage differential backups simplify the
  restore process.
• Disadvantage differential backups use more tape,
  because some of the same files are backed up each
  day.

19
Scheduling

• All backup products let you create a backup job
  and execute it immediately.
• The key to automating a backup routine is being
  able to schedule jobs to execute unattended.
• Scheduled jobs can run when the office is closed
  and the network is idle.
• Not all of the backup programs supplied with
  operating systems or designed for stand-alone
  computers will support scheduling, but all
  network backup software products do.
• Backup programs use various methods to
  automatically execute backup jobs.
• You specify whether you want to execute the job
  once or repeatedly at a specified time each day,
  week, or month.
• After creating a logical sequence of backup jobs
  that execute by themselves at regular intervals,
  you only need to change the tape in the drive
  each day.

20
The Schedule Job Dialog Box in the Windows 2000
Backup Program
21
Logging and Cataloging

• Most backup software products can maintain a log
  of the backup process as it occurs.
• You can often specify a level of detail for the
  log.
• You should periodically check the log, which
  tells you
• When selected files are skipped for any reason
• When errors occur on either the backup drive or
  one of the computers involved in the backup
  process
• Backup software programs also catalog the files
  they back up, which facilitates the process of
  restoring files later.
• The catalog is a list of every file that the
  software has backed up during each job.
• To restore files from the backup medium, you
  browse through the catalog and select the files,
  directories, or drives that you want to restore.

22
Media Rotation

• Using new tapes for every backup job and storing
  them all permanently can become extremely
  expensive.
• It is more common to reuse backup tapes.
• To reuse tapes properly, you must carefully plan
  your media rotation scheme.
• The Grandfather-Father-Son media rotation scheme
  refers to backup jobs that run monthly, weekly,
  and daily, and it requires you to maintain
• A set of tapes for daily jobs, which you reuse
  every week
• A set of weekly tapes, which you reuse every
  month
• A set of monthly tapes, which you reuse every
  year
• When the software program implements the rotation
  scheme, it
• Provides a basic schedule for the jobs
• Tells you what name to write on each tape as you
  use it
• Tells you which tape to put in the drive for each
  job

23
Restoring

• You must perform periodic test restores from your
  backup tapes or other media to ensure that you
  can recover any lost data.
• Even if all your jobs are completed successfully
  and your log files show that all of your data has
  been backed up, there is no better test of a
  backup system than an actual restore.
• Most of the restore jobs you will perform will be
  restoring only one or a few files that a user has
  deleted.
• A backup program with a database that lets you
  search for a specific file makes your job much
  easier and enables you to restore any file in
  minutes.

24
The Restore Dialog Box in the Windows 2000 Backup
Program
25
Network Backup Functions

• Choose a backup software product that is designed
  for network use.
• A network backup software product differs from an
  application designed for stand-alone systems in
  that the network product can back up other
  computers on the network.
• A fully functional network backup product can
  back up drives anywhere on the network, plus
  important operating system features on other
  computers, such as the Windows Registry and
  directory service databases.
• Network backup products often have optional
  add-on components that let you perform
  specialized backup tasks, such as backing up live
  databases or computers running other operating
  systems.

26
What Is a Virus?

• A virus is a software routine that is
  deliberately designed to attach itself to another
  piece of software on a computer, perform some
  preprogrammed activity, and spread to other
  computers on the network.
• The worst types of viruses are engineered to
  irretrievably destroy all or part of the data
  stored on the computer by wiping out hard drives.
• Potentially damaging programs such as viruses,
  Trojan horses, and worms can find their way onto
  a network through file downloads, e-mails, or
  even removable disks.
• Like biological viruses, computer viruses are
  designed to replicate themselves by infecting
  other pieces of software.
• A virus on an infected removable disk can migrate
  to the computers hard drive and infect the code
  on the hard drive.

27
How Viruses Can Spread Throughout a Network
28
Virus Types

• Boot sector viruses
• Executable file viruses
• Polymorphic viruses
• Stealth viruses
• Macro viruses
• Worms
• Trojan horses

29
Preventing Virus Infections

• All users should be wary of removable disks from
  outside sources and particularly of files
  attached to e-mail messages.
• You should use antivirus software products to
  protect individual computers.
• A virus scanner works by examining files and
  searching for specific code signatures that are
  peculiar to certain viruses.
• The scanner has a library of virus definitions
  that it uses to identify viruses.
• To keep your computers fully protected, you must
  update the virus signatures for your program on a
  regular basis.
• Antivirus programs designed for use on networks
  do not provide greater protection against
  viruses, but they simplify the process of
  implementing the protection.

30
Major Updates

• Even a computer with a relatively simple
  configuration can have many different software
  components that are regularly updated.
• Years ago, operating systems manufacturers would
  release many different software patches, each
  addressing a specific issue.
• Now manufacturers release groups of updates in a
  single package.
• This practice was pioneered by Microsoft with its
  Service Pack releases for Microsoft Windows NT.
• Each Service Pack release for a product contains
  a collection of patches and updates, all of which
  are applied by one installation program.
• Because the various patches have all been tested
  together, the operating system environment is
  consistent.

31
Patches

• Between the releases of Service Packs or other
  major software updates, manufacturers may also
  make individual patches available.
• A patch is usually a small fix that is designed
  to address a highly specific problem.
• In some cases, manufacturers recommend that you
  install a patch only under certain conditions,
  such as when you are using a particular
  combination of components or when you are
  experiencing a specific error.
• If your environment does not qualify, do not
  assume that you should install the patch anyway,
  just to keep your software current.
• Read all of the release documentation and
  carefully follow the manufacturers instructions.

32
Software Upgrades and Updates

• Software manufacturers typically release periodic
  upgrades.
• An update is usually a relatively minor release
  that addresses specific issues or provides modest
  enhancements.
• An upgrade is a major release that provides new
  features and capabilities.
• In most cases, patches and updates are free, but
  you must buy an upgrade.
• The cumulative cost of the upgrade process can be
  enormous.
• If you do not need new features, it might not be
  worth upgrading.

33
Chapter Summary

• Backups
• Magnetic tape is the most popular storage medium
  for backups.
• Backup software enables you to select the data
  you want to back up and sends it to the device
  you use for backups.
• Daily backup jobs can be full backups,
  incremental backups, or differential backups.
• A good backup software program allows you to
  schedule jobs to execute at any time.
• Network backup software enables you to back up
  data from computers anywhere on the network, and
  might also provide optional features such as live
  database backups.

34
Chapter Summary (Cont.)

• Antivirus policies
• Viruses are dangerous programs that can damage
  the data on a computer and spread to the other
  computers on a network.
• To protect your network against viruses, you must
  run antivirus software on every computer.
• Patches and updates
• Obtaining, evaluating, and deploying software
  patches and updates is an important part of the
  network administrators job.
• Software upgrades are major undertakings that can
  be extremely expensive and time-consuming.