It's not clear what you mean. If we have two components, one of which is 99% available and one of which is 100% available, the second is not 1% better than the

It's not clear what you mean. If we have two components, one of which is 99% available and one of which is 100% available, the second is not 1% better than the first. It is infinitely better than the first. It's well understood in reliability engineering that, at least in the long term, the cost of availability increases exponentially as the goal approaches 100%. Buying more expensive hardware (with better per-component availability) is one approach to a full availability picture. However, it's one with significant shortcomings. At the top end, it's very expensive. Across the board, it only addresses some possible threats, and completely doesn't address others (like natural disasters). The alternate approach is redundancy. That approach is not without it's shortcomings, including increased system complexity and the problems of failure detection and failover. However, it's generally lower cost and is more robust to multiple types of threats. This is why RAID is so successful - because it is a reliable set of techniques for building highly-reliable systems out of unreliable components. Again, it only protects against one threat (drive failure) and not others (fire), but it's proven superior to the alternative "buy a single gold-plated drive" approach. Low-end gear isn't for everybody. Cutting corners in the wrong places is dumb. On the other hand, high-end gear only saves you in some ways, and those ways may not matter to your business. If you want high-availability or high-durability you need to know to things: how much your data is worth, and what you are protecting it from. Until you know these answers, you're going to be making poor system design decisions.