??? Service.availability??”Customer-centric.focus.(service.orientation):.The emergence
of the Service Availability model as a driving concept in system design represents a
shift from a technology-centric orientation to a customer-centric one. A service availability
solution includes providing high availability at the level of 5-Nines or better,
but it adds the requirement of service continuity, maintaining the integrity of customer
connections and transactions without interruption despite any hardware or software
failures in the infrastructure. Neither scheduled maintenance nor unexpected failure
ought to prevent or disrupt provision of service to a customer. A service availability
solution requires that a system be highly available and provide continuity of service. A
system configured with redundant components that fail can switchover to the standby
components without ultimately jeopardizing the metrics of reliability or availability,
0 Rada deh & Al-Ameed
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even though connections might be dropped or data lost or degraded. Thus, a service
availability solution carries the caveat that, during switchover scenarios, customer
data and application state must be preserved in order to provide continuity of service
to the end-user.
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