Nov 15, 2024 · 4 min read
Redundancy is the practice of duplicating critical components or functions of a system to increase reliability. The principle is simple: if one component fails, another takes over. However, implementing effective redundancy requires careful planning and understanding of failure modes.
N+1 redundancy means having one more component than required for normal operation. For web servers, this might mean running three instances when two can handle the load. This approach balances cost against resilience, providing a safety margin without excessive over-provisioning.
Data redundancy through replication ensures that information survives hardware failures. Database replication, whether synchronous or asynchronous, RAID configurations for storage, and backup strategies all contribute to data durability. Understanding RPO and RTO requirements guides these decisions.
Network redundancy involves multiple paths for data to travel. This includes redundant switches, multiple uplinks, and diverse internet connections. Protocols like LACP for link aggregation and routing protocols that can failover between paths provide automatic recovery.
The key challenge with redundancy is testing. Redundant systems must be regularly verified to ensure failover works as expected. Chaos engineering practices—deliberately introducing failures—help validate that redundancy mechanisms function correctly under stress.
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