Difference between revisions of "System availability"
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|99.999%||5||5||minutes/year | |99.999%||5||5||minutes/year | ||
| + | |} | ||
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| + | ==System Downtime== | ||
| + | '''Many events causes system downtime:''' | ||
| + | *HW fault | ||
| + | *Software fault | ||
| + | *Vandalism | ||
| + | *Extreme conditions (fire, flooding etc) | ||
| + | *Power outage | ||
| + | *IP network failure | ||
| + | *Planned system maintenance | ||
| + | <br> | ||
| + | <br> | ||
| + | '''System Downtime = ∑ P * S * MTTR''' | ||
| + | {|border="0" | ||
| + | |width="60px"|P | ||
| + | |= Probability of event taken place | ||
| + | |- | ||
| + | |S||= Severity of event | ||
| + | |- | ||
| + | | ||= Percentage of service affected by fault | ||
| + | |- | ||
| + | |MTTR||= Mean Time To Repair | ||
| + | |- | ||
| + | | ||= mean time to detect fault + mean time to fix fault | ||
|} | |} | ||
[[Category:AlphaCom E System]] | [[Category:AlphaCom E System]] | ||
Revision as of 13:56, 4 August 2009
System availability
System Availability
- The percentage of time that the system can perform its intended function
System Availability = 1 – System Downtime
Downtime per year
| Availability | Nines | Downtime | |
| 90% | 1 | 36.5 | days/year |
| 99% | 2 | 3.65 | DAys/year |
| 99.9% | 3 | 8.78 | hours/year |
| 99.99% | 4 | 52 | minutes/year |
| 99.999% | 5 | 5 | minutes/year |
System Downtime
Many events causes system downtime:
- HW fault
- Software fault
- Vandalism
- Extreme conditions (fire, flooding etc)
- Power outage
- IP network failure
- Planned system maintenance
System Downtime = ∑ P * S * MTTR
| P | = Probability of event taken place |
| S | = Severity of event |
| = Percentage of service affected by fault | |
| MTTR | = Mean Time To Repair |
| = mean time to detect fault + mean time to fix fault |