Backups : Backup Strategy

A backup strategy is a plan which details how backups will be made and how data will be restored in the event of a system failure. There are many important factors that should be considered in a backup strategy. These include :

• How often should data be backup up ?
• When should data be backed up ?
• What storage medium should the backups be stored on ?
• Where should backups be stored ?
• Should backed up data be compressed ?
• Who will carry out the backup procedure ?
• What will happen if data is lost ?
• How many copies to keep ?

How often should data be backup up ?

If a file is corrupted and you restore the file from a backup copy then some data may still be lost. This is the data that was added to the file since the backup was made. If backups are made once a week then a whole week's work could be lost. On the other hand if backups are made once a day then only a day's work would be lost. Backups should therefore be made as regularly as possible.

Unfortunately backups cost money to produce. Storage media must be purchased and staff time is taken up. Therefore a balance has to be struck between making backups very frequently and keeping backup costs down.

As a general rule files which change frequently should be backed up often whereas files which do not change very much can be backed up less frequently.

When should data be backed up ?

Backing up data can tie up a computer so that it can not be used whilst the backup is in progress. Therefore backups are usually made overnight or at weekends when a computer system is less likely to be in use.

What storage medium should the backups be stored on ?

There are a variety of different storage media that backups can be stored on. These include magnetic and optical disks and magnetic tapes. The best medium to use in a particular situation will probably depend upon the volume of data to be backed up and the speed at which the backup must be performed.

• Floppy Disks : Only suitable for backing up small amounts of data (1.44Mb) and very slow. Some high capacity floppy disks which can store up to 250Mb are know available. These can store more data but are still relatively slow.
• Optical Disks : Optical disks such as CD-RWs can back up much more data than floppy disks but not as much data as a tape. Typical capacities are around 650Mb. They are much faster than floppy disks but not as fast as magnetic tapes in most circumstances.
• Magnetic Tapes : These are suitable for backing up large volumes of data (tens of gigabytes). The backups can be performed very quickly. Tapes are very cheap to buy but the initial cost of the hardware required can be high.

Where should backups be stored ?

There is no point in making a backup copy if the backup may be damaged. These guidelines should be followed to ensure that backups are stored safely :

• Store at least one backup at a site away from the main computer system. If the main system is damaged by a natural disaster such as a fire then the off site backup will be safe. Any backups kept on site may be destroyed.
• Control access to backups so that unauthorised personnel can not remove them or steal data from them.
• Keep backups in a clean, dust-free environment so that the medium that the backups are stored on will not be damaged.

Should backed up data be compressed ?

Data that is backed up can be compressed to reduce the amount of storage space that it will require. Compressed backed up data must be decompressed before it can be restored. Therefore backups are usually only compressed if they are unlikely to be accessed regularly.

Who will carry out the backup procedure ?

In a small company each employee may make his or her own backups. In a larger organisation however the task of producing backups will usually be performed by one selected individual. This individual can be properly trained in using the backup procedure and can keep accurate records of the backups that have been made.

What will happen if data is lost ?

If data is lost then it will have to be restored from the backup. A disaster recovery plan should be in place which describes how the data will be restored.

How many copies to keep ?

It is a good idea to make more than one backup copy. This gives you the extra assurance that if a file is corrupt and the backup is also corrupt then you have another backup which may still be operational.

GCSE ICT Companion 04 - (C) P Meakin 2004