Availability
Measuring high availability metrics, redundancy models, active-passive failover strategies, and "The Nines" SLA standards.
What you'll learn
- The Nines
- SPOF (Single Point of Failure)
- Redundancy
TL;DR
Measuring high availability metrics, redundancy models, active-passive failover strategies, and "The Nines" SLA standards.
Concept Overview
Availability is the percentage of time a system remains operational, reachable, and capable of executing user transactions. High Availability (HA) ensures systems survive hardware and network outages.
Key Architectural Pillars
The Nines
Uptime percentage bounds: 99.9% (3 nines = 8.76 hrs downtime/year) vs 99.999% (5 nines = 5.26 mins downtime/year).
SPOF (Single Point of Failure)
Any isolated hardware component or software service which, if crashed, brings down the entire application.
Redundancy
Duplicating critical system components so that standby instances instantly take over during primary outages.