Hst 4.2 Availabilty percentages and intervals

Availability Levels - SLA
1. Uptime in period of time in month/year
  1. 99,8%
  2. 99,9% (3 nines)
  3. 99,99% (4-nines)
  4. carrier grade availability = extremely high availability
    1. 99,999% (5-nines)
MTBF = Meam Time Between Failures
1. average time that passes between failures
2. expressed in hours, how many hours will the component or service work without failure
  1. MTBF = (see boek page 55 for example.)
MTTR = Mean Time To Repair
1. which is time to take to recover from a failure
  1. manual actions
    1. components repair
      1. notifications of the fault
      2. processing alarm
      3. find root cause of error
      4. looking up repair information
      5. spare componenets from storage
      6. technician to datacenter for repair
      7. restarting and testing the components
    2. components replace
Availability =
1. 1. calculation example see boek page 56-57
2. serial availability
  1. when a failure of any part in a system cause a failure of the system as a whole
    1. system with serial components
    2. to increase availability
      1. Two systems in parrallel

Zusammenfassung der Ressource

	Erstellt von G. Wagenmaker vor etwa 7 Jahre