Policy & Strategy : Back-up Strategies
The factors that need to be considered when a large company is devising a backup strategy for its information systems are:
- Frequency - how often the data on the system changes will affect how often the backup needs to be made.
- Storage - the backup needs to be stored safely and securely from the main system(s).
- Volume - the backup needs to take into account how much data there is e.g. for how long the backup will take.
- Personnel - who is going to conduct the backup, so that the company can be confident that the backup has occurred.
- Logging - will there be a record indicating when the backup has taken place, and any problems that may have occurred?
- Testing - integrity of the backup needs to be ensured, so that if it needs to be recovered it can be relied on
- How critical the system is - can the system be taken offline in order to backup?
The types of Backups
A full back-up is a copy of all data and software. This is the safest way of doing it because there is a copy of every program and every data file. An organisation, depending on the amount of data may take a very long time to carry out a full back-up, during which time nothing can be done on the system.
An Incremental Back-up backs-up only the data that changes since the last full back-up or the last incremental back-up. This is less time consuming than a full back-up, but more complex to restore, as all back-ups have to be done in the right order.
An On-Line Back-up allows an organisation that cannot afford to lose even a few seconds worth of data to back-up as they work. They may well use RAID systems with possibly a hard-drive in a remote location. Should a drive fail, software allows other drives to be accessed, and all the data are available. The disk in the remote location allows data to be accessed in the case of some severe event at the main processing centre (e.g. a bomb).
Grandfather-Father-Son Back-ups is where four generations of back-up file are kept, before the oldest is overwritten. If the most recent back-up is faulty then the previous back-up can be used.