Reliability in terms of Computer Systems

Reliability in terms of Computer Systems

1. How can reliability be measured?

   • AVAIL: The percentage of time that the system is available to the user/customer but taking out any planned 'downtime' for maintenance etc. (Available hours divided by planned hours x 100)
   • MTTF: Mean time to failure (also referred to as MTBF: Mean time before failure. This is the average number of hours a system can run before breaking. Tends to be measured for hardware.

2. What is reliability?

   • Reliability is being confident a system can perform the expected actions, and when referring to computer systems, can be measured using a metric. A metric tends to be an average measure

3. Personal effect

   • Many peoples personal computers hold a large amount of important information, whether it be memories, photographs or document (school work etc)
     • If this information was to be lost, a 'backup' system would be a very good idea.

4. Financial/business effect

   • Many major business' computer systems will hold a lot of vital information, whether it be personal information of the public or information needed to keep the business steady.
     • A loss of this information could potentially be the downfall of the business.

5. How can reliability be improved?

   • Realibility can be improved using redundancy - this is the duplicaitaion of ciritical parts of the system that would need to be swifltly restored if the system was to break down. if it was to fail then these components or sub-systems wouid take over. For example, the power supply to a rack may be duplicated. If the power began to sag due to component failure, then the other power supply would kick in.
     • Data redundancy is a different concept. This includes duplicating the data in more than one location within the computer system rather than storing the information in a different device. This is useful when one single component fails, meaning the data is not completely lost. This can be achieved by running two hard disks in parallel, both storing the same data. This is known as RAID 1 or 'disk mirroring''. If one hard disk fails, an alert is sent and the other instantly kicks in,.

6. Single machines

   • For the individual or small office running non-server personal computers, it is a good idea to backing uphave an attached external hard drive and a good backup application running on each machine

7. Network servers

   • For a file server, it is standard practice to back up to digital tape machines or to replicate the data on a remote server

8. Data centres

   • For large organisations, such as a building society, an entire data centre may be duplicated in a separate location.

9. Cloud backup

   • Another option is to hire an external specialist in data storage. Every night, the individuals/business' information is uploaded to the data centre. This is becoming an increasingly popular method due to being very cost effective, and useful for smaller business' or companies.