Resiliency - 3.4
High Availability
Redundant systems might not be available for immediate use. High Availability means that in the event of a failure, we can experience zero or minimal downtime.
Clustering
The practice of using multiple servers as one, where the clustered group of servers acts in a synchronous way to provide redundancy and high availability.
Load Balancing
Similar to clustering, but multiple servers act independently, and the load balancer is responsible for distributing requests to them to optimize resource use and prevent overload.
Site Considerations
- Hot Site: An exact replica of a site, including hardware, software, data, and configurations, ready for immediate use in case of a disaster.
- Cold Site: A location with utilities and basic infrastructure but no pre-installed hardware, software, or data. Requires setup before becoming operational.
- Warm Site: A mix of the two; some hardware and software are pre-installed, and some data may be available, but additional setup is needed to become fully operational.
- Geographic Dispersion: Distributing backup sites away from the primary site to prevent both sites from being affected by the same disaster, such as natural events.
Platform Diversity
Using multiple operating systems and devices means that if a failure or vulnerability is present in a specific platform, other platforms might not be affected, enhancing overall resilience.
Multi-cloud Systems
Similar to platform diversity, using multiple cloud providers can reduce the risk of failure in case one of these services or providers fails.
Continuity of Operations Planning (COOP)
Planning to ensure essential functions continue during and after a disaster when technological backups may not be available. COOP involves strategies to maintain services and operations, possibly through non-technical means.