8745941
Description
Flashcards by Josh Watkins, updated more than 1 year ago
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Created by Josh Watkins
about 7 years ago
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| Question | Answer |
| The five things that can go wrong with a computer system | hardware failure software failure human error malicious damage natural disasters |
| Some of the consequences of non-life-critical systems failing | Loss of revenue Dissatisfied customers Damage to reputation Fines for breaking the law |
| Examples of critical systems | Utilities Supplies Banking Emergency services Telephone network Food supply Air traffic control Nuclear safety |
| Some consequences of critical systems failure | Risks lives of customers Put business to a halt |
| Malicious intent with a critical system | Cyber-terrorism Cyber terrorists are hard to catch and prosecute when operating in another country |
| Types of backing-up data | Full backup: makes a copy of everything Incremental backup: only makes a copy of new or edited files |
| Backup Procedure | A backup schedule should be in place and there should be someone in charge of it. Backup sites should be off of the main companies site in a locked, fireproof place |
| Disaster Recovery Definition | Getting a system back to normal after a large-scale failure. |
| Disaster Recovery Procedure | Most organizations have a disaster recovery plan. After a system failure, data must be restored from a backup. |
| Redundancy Definition | Have duplicate resources or extra resources that can support the main system. A backup system for if the main one goes down |
| Three main types of redundancy | Hardware like reserve storage or servers Software like a backup OS Data (already covered this) |
| Parallel Setup | Have two identical hardware setups that allow the company to switch between one and other, reducing disruption to their normal operations |
| Fault-tolerant Design | If parts of the system fail the system is designed to be able to continue running or 'fail gracefully' if it needs to completely stop |
| Failing Gracefully | The system will take steps to avoid data loss when things begin to go wrong. This could be writing an emergency copy of data before shutting down unexpectedly. This emergency copy is called a 'dump file' |
| Defensive Programming | Adding checks to see if the program is running properly. This can warn a user of a fault to prevent unexpected crashing |
| Measuring Reliability |
Percentage of time working
Number of hours operating without issues
Downtime
Mean time between failures
Mean time to fail
Image:
Large (image/png)
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| Alpha Testing | Unit testing - checks a program's components Validation Testing - checks the type of data that can be used Volume testing - checks the amount off data a system can handle |
| Beta Testing | Users warn the programmers of any problem and the programs can be fixed and updated weekly or monthly for example |
| End-users | Users can find unexpected problems with a system. Updates are then released. Some companies reward people for finding problems e.g. Facebook |
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