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Data Backup and Archiving
Frequently Asked Questions
Inside...
See also...
Protect your investment in hardware, software and data!
What is a backup?
A backup is a safe and accurate copy of the information stored on your hard
disk made onto an independent storage medium such as a tape, a diskette or a
recordable compact disk. A backup can be a complete copy of all the files on your
hard disk including system and hidden files, application files and data files, or
a partial copy incorporating just some of these files. A full backup of your
system will include all the files that you have Created plus all the files that
control the way your PC operates.
Why do I need to backup my data?
It is essential that you make regular backups to protect your investment in
hardware, software and data. Having an up-to-date copy of all your data will
protect you in the event of data loss through accidental deletion or corruption
of files, hard disk failure, or virus attack. In the event of such a crisis, it
will provide you with a safe and reliable means of recovering your data, allowing
you to restore your system to its pre-crisis state in the shortest possible time.
To find out the kinds of problem you might encounter, see the section entitled:
Examples of what can go wrong
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How is a backup made?
There are several ways to make a backup. All involve copying the contents of
your hard disk onto a separate storage device. This can be done either from MS-DOS
using BACKUP.EXE, from Windows 3.1 using MWBACKUP.EXE, or from Windows 95/98 by
selecting Backup from the Start menu (located in Programs\Accessories\System Tools\Backup).
Alternatively, if you have a backup drive, you can use a proprietary software
package such as HP Colorado Backup.
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How often do I need to do a backup?
You need to backup your data as often as you use your computer; every day if
you use it every day. There is no telling when disaster may strike. However, you
don't need to do it all in one go. For example, you might choose to make regular
weekly backups and then backup only those files which have changed on a daily
basis (the operating system keeps a record of these).
How can I recover my data once it is lost?
Without a proper backup, it may take you hours or even days to recover your
data. Indeed, some information may be lost for ever.
If you have made regular backups of your system then you can reload the
information you require from your backup, either in full or just the files you
have lost.
What is a backup strategy?
A backup strategy is your way of planning for future data loss whether it be
through accidental deletion, virus attack or hardware failure. Your choice of
strategy depends very much on what sort of system you have, what you use it for
and how often you use it. For example if you use your PC only occasionally then
you will need to make one or two complete backups of your system and copy only
those files which have changed on a regular basis. If, however, you use your
computer intensively in your work then you will need to make regular full backups
of your system onto two or more data storage sets.
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What strategy should I choose?
Selecting a suitable backup strategy involves choosing the
type of storage device which is appropriate and the type of media to use. In
practice, this depends very much on the capacity of your hard disk and the amount
of information you have stored on it. Thus if you have 20 megabytes of data, this
can be backed up easily onto diskette. If, however, you have 200MB, then backing
up onto diskette is inappropriate as it will take nearly a hundred diskettes and
several hours to complete. It will also cost you nearly £70 per backup set. For
backups involving more than 50MB of data, tape is the most appropriate medium.
Depending on the type of tape you use, it is possible to store anything upwards
from 200MB to several gigabytes on a single tape.
You also need to identify any old or redundant data so these can be archived
to tape or disk.
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How can I plan for future problems?
1. Prepare a Disaster Contingency Plan
This should comprise complete system inventories of all your hardware and
software, including model numbers, version numbers and serial numbers, and
important system set-up information. In the case of a network, it should also
include a map of network connectivity. This information needs to be kept up to
date.
It should also include a fast emergency start-up plan consisting of procedures
for hardware and software procurement, data restoration, and if necessary site
rental. Again this plan needs to be kept up to date as hardware and software
requirements change.
A copy of the disaster contingency plan should be stored off-site.
2. Set-up a 3-tier Data Backup Strategy
This should consist of a documented backup system with numbered media and a
record of what tapes were used in which backup on what day. To provide historical
continuity, a three tiered system should be implemented, incorporating:
- High frequency periodic backups (e.g. daily);
- Medium frequency backup retention (e.g. save the Friday's backup until next
week);
- Low frequency backup retention (e.g. save the first backup of the month till
next month).
Backup sets should be tested periodically to make sure that they work. Low
frequency backup sets should be stored off-site.
3. Define a Strategy for Archiving Old or Redundant Data
This involves copying old and infrequently used but non-the-less sensitive
data to backup media for permanent storage (and if applicable the applications
needed to access them). Archiving usually involves deleting the original from the
source machine so that the copy is the only one in existence. Depending on volume
of data, backup media may comprise tape or recordable CD (CD-R).
If using magnetic media, two copies should be made and the backups tested prior
to deleting the source data. Archive tapes should be refreshed periodically,
usually once every twelve months, to ensure the recorded data does not fade. Tapes
for long term storage should be stored away from extremes of temperature and
humidity.
Recordable CDs have a much longer life than magnetic media, with an expected
life of twelve years. An archiving strategy based on recordable CD-ROM is
therefore preferable.
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I accidentally deleted a section of text in my word processor.
I didn't realise it at the time but I'd selected a section of text I wanted to
move when I must have pressed the delete key by mistake. By the time I'd noticed
the error, I'd already saved my work. It took me a couple of hours to retype the
information.
I accidentally deleted some important system files.
I was using File Manager to delete some unwanted files. I must have selected
some of the files in the Windows directory as well because the next time I came
to use the Control Panel, I noticed several of the utilities were missing. To
correct my error I had to reinstall Windows 3.0 and then Windows 3.1 as I only
had the upgrade disks. In the process, I lost all my system settings and had to
reconfigure Windows.
I accidentally corrupted some important files.
I downloaded some shareware from the Internet and ran the set-up program. The
software copied some .DLL files into my Windows\System directory. However, one of
these files must have been an earlier version of the one used by my fax software
because the latter no longer worked. It took me ages to diagnose the problem.
Eventually, after phoning product support, I reinstalled my fax software which
seemed to solve the problem.
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Archiving versus Backing up
Archiving involves copying information from your hard disk to an appropriate
storage device before deleting the original, thereby releasing space on your hard
disk.
An appropriate storage device might be a tape drive or recordable compact disc
drive (CD-R). Bearing in mind the relative life expectancies of magnetic media
(1 to 2 years) and optical media (up to 12 years), a CD-R drive is probably the
best choice.
Particularly if you are running out of space on your hard drive, you might
decide to archive the information you access least frequently. Information that
is one or two years old or old versions of software that you no longer use are
ideally handled in this way.
There are a wide variety of backup devices to choose from, including tape
drives, CD-R drives, and removable disk drives. Your choice of drive depends
largely on the amount of information you need to backup, and what you are going
to do with that information once you have backed it up.
For most uses, tape is still the most appropriate medium. However, if you want
to distribute copies of information to colleagues, you might also consider
purchasing a CD-R drive. If, however, you want to share information between two
machines, for example one at home and one at work, then you might consider
purchasing a removable disk.
When buying a backup drive, you must always plan ahead for any new equipment
you might need to buy in the future such as a new PC or hard disk. If you are
buying a network drive, then you must also consider the number and storage
capacities of each machine on the network.
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