5-Nines.Availability.
The 99.999% (5-Nines) availability standard specifies 24/7 service with a maximum of
five minutes of downtime in a year. Generally, service availability depends heavily on the
fault tolerance of the system, including hardware redundancy (Klein, 1988). The software
components of the system use the redundant hardware to enable the service and application
availability. 5-Nine implementations have its foundation in the set of principles. Some of
these principles are related only to hardware, while other principles are related to software
system components. The following list of issues focuses on providing the service high
availability (Parikh, 2004):
??? Mitigation.of.risks:.Risk mitigation depends on monitoring (real-time and historical)
trends, rules, and models to predict the occurrence of failures and to prevent them.
Common risk mitigation techniques are:
o Fault.avoidance: use of processes and tools to minimize the introduction of
faults;
o Fault.minimization: In spite of efforts to prevent or eliminate them, there will
be faults in any system. Proper risk assessment and fault minimization can ensure
uptime; and
o Fault.recognition.and.removal: Monitoring and recognition can actively locate
faults and assist with remediation of their root cause.
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