The Issue

The most important component of an information system is the data that it contains. Without its data the system would be unable to produce any information, which would make users question the need for the system. 

It is easy to replace faulty hardware in the event of hardware failure, and if the controlling software doesn’t work it can always be reinstalled, however, if the data is lost or corrupted it is very difficult to do anything unless you have a copy or a backup of the data.

Data is also supremely important to a business. Find our how much data is worth to a business by viewing this site http://www.edms.net/news/howmuch.htm

To prevent data loss caused by system failure computer users should have backup procedures. A backup is a copy of information stored on a computer. The backup copy can be used to restore (or reload) the data files on to the computer. There is a lot of facts and figures about backup, so we will start with a light hearted look at backup found at http://www.taobackup.com/index.html

From this site record the 7 factors (or lessons) you need to consider about backup.

1.BACKUP MEDIUM & STORAGE OF MEDIUM

Deciding where to store your backup is directly related to the threats that you want to protect against. We will assume that the data to protect is stored on a PC’s local or server hard-disk drive.

It is not wise to store the backup in the same location (PC’s local or server hard-disk drive) as the original, as it is still at risk from the same viruses, hardware failure, and other disasters such as theft and fire, as the original data.

This tends to suggest that we should backup the data using a removable storage device. Options that might be considered are the floppy disk, removable magnetic disks or disk cartridges (eg. ZIP drives), and CD – RW.

As all these options are portable, the final choice is dependent on cost, speed and quantity of data to be stored. The cost can be attributed to the price of the removable device, as well as the cost of consumables and whether they can be reused, and if so how often can they be reused.

In addition, the speed taken to backup data needs to be considered. If backup is critical then the time taken to backup the data needs to be economical, otherwise a person will not consider doing this on a regular basis.

Another important factor is the quantity of data to be stored. A backup of a school project might be performed on a floppy disk, as the project file may be less than 1.44Mb, (although a larger file could be compressed onto the floppy using a file compression program such as WinZip). However, an alternative needs to be found for larger files, so the magnetic disks or disk cartridges may be preferable.

2. TYPES OF BACKUP

To be of any use, a Backup needs to be performed on a regular basis. The business also needs to determine whether a full or partial backup is required at this time.

A full backup backs up all the files in a given directory or computer. This can take a long time in there are large and numerous files on the system. However, all data can be recovered in the event of a system or data failure in the fastest time.

A partial backup backs up only the files that have been changed since the last backup. If recovery is required, you still need the last full backup plus the partial backup.

If a database is created using Microsoft Access, all information is stored in one file. A change to the database means that the entire file has changed, so that in most instances a full backup is required.

3. PROCEDURES FOR BACKUP

A business should have some procedures in place that document how often a backup is performed. Ideally, it should be performed at a regular time each day/night, preferably at the end of the day, as all changes have been finalised.

This can be performed manually by the operator / system manager or there are many commercial backup software packages available that will schedule this task and perform it at a non-busy period. A look at some backup software and the different modes of backup can be found at How Stuff Works.

Software Available

For individual users, Microsoft Windows has it own backup software (called Backup), accessible from Start\ Programs\ Accessories\ SystemTools \ BackUp  or look at how to backup your Home network using Windows XP

Both methods allow you to choose the files that need to be backed up. It will compress the files to conserve storage space and backup the selected files onto your choice of backup media, such as a network drive, a removable ZIP disk or a floppy disk.

If a database is stored on an individual hard-drive the individual will need to backup their data onto a network drive. The network drive is then regularly backed up. If the database is stored on the network then it should be automatically covered in the daily backup, however it is prudent for the user to take an additional backup.

How often to backup

Each day’s backup should be stored on a separate disk/tape. Monday’s backup is stored on Monday’s tape, Tuesday’s backup on Tuesday’s tape and so on. On the next Monday, the backup is saved over the existing Monday tape. This way a complete week’s backup is saved. In this instance, the most work or data files that will be lost will be one day’s worth – which will need to be reworked.

In addition, some system managers take a further backup at the end of each month and store this on CD-ROM, and may even do this again at the end of each year.

Review the points discussed above by looking at the following site http://deepee.idx.com.au/data_backup.htm

Your Task

If you have visited the sites described above, you should have sufficient background, to answer the following:

4.  PROTECTING DATA FROM WHAT THREATS?

To fully understand why you should protect your data by backup, we will need to understand the threats to the data in an information system and investigate how data can be damaged.

Protection can take the form of setting up controls that stop the data from being corrupted, damaged or lost.

Data can be damaged in the following manners, through:

These will be covered in more detail when we start to study Databases.