High availability(HA) means undisrupted functioning of a system for a long time so that users face no troubles in accessing the system almost all the times. Customers expect from companies that their services will be highly available 24x7x365, especially when services that are linked to life, health, well-being etc could be paralyzed due to system failures. It’s important to note that high availability does not mean a system will never face a failure. HA means a system that is designed to manage failures and minimize downtime (time period for which system service is not available) so that services can be restored with negligible adverse impact on users. Uptime is used for a time period during which a system is in operation.
A system failure occurs due to failures of components in the system, resulting into downtime and non-availability of system resources, which is technically called as an outage.
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