Redundancy
Also known as: Fault Tolerance · Failover
Redundancy means a critical component exists twice or more, so the failure of one part does not interrupt operations.
Redundancy means a critical component is not present just once but doubled or duplicated further, so that when one part fails, another takes over automatically or with little effort. It exists because individual components such as hard drives, power supplies, or internet lines eventually fail, and a business with no fallback simply stops when they do.
In practice, redundancy shows up in RAID systems, where data is spread across multiple drives so that RAID 5 can survive the failure of a single drive without data loss, or in two independent internet connections from different providers with automatic failover between them. Dual power supplies in a server, or two switches that can each carry the same load, are also common forms.
A common mistake is fake redundancy: two internet lines that actually enter the building through the same cable in the same trench, or two UPS units plugged into the same circuit breaker. Real redundancy requires that the components can genuinely fail independently of each other.
What it means in practice
Missing redundancy usually only becomes visible when the one drive, line, or component without a backup fails, and operations grind to a halt as a result. NDVDL weighs, on each server room project, where real redundancy is worthwhile and where it would not justify the cost.
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