HA, or High Availability, is outside the scope of more small businesses; however, it is frequently misunderstood and abused by salespeople.

HA includes redundancy and extends it to cover all the parts that could fail and cause an interruption. Instead of two systems being connected by a single network cable, they each have multiple network cards to allow four cables (through two redundant network switches). In practice, assume that the hardware required will be 10-50x more expensive before you even consider extra power and cooling expenses. That’s assuming that critical applications can even utilize HA -- developing HA friendly software for multiple users is significantly more difficult. You may even end up needing a full time systems person and database administrator (DBA).

However, you can achieve a highly redundant system that requires a minimum of supervision if you can accept brief outages to restart a system on redundant hardware. It’s usually the difference between 99.9% uptime and 99.999% uptime.