Its easy to spend a lot of money chasing the wrong definition of system availability. If I were selling processors, Id tell you that uptime comes from clusters and CPU failover mechanisms. If I were selling storage, Id tell you that consistent response depends on storage area networks and speedy switching.
In customer-facing applications, however, the perception of high availability may be almost at right angles to the reality. If that expensive high-availability hardware is up and running, but the inventory systems arent well coupled with the order-taking processes, then customers may waste time ordering items that cant be shipped until after theyre needed. When a customer has crossed off an item on a list, only to get an e-mail four days later that says the item isnt available after all, thats not just a lost sale: its probably a lost customer as well, perhaps with multiplier effects due to negative word of mouth.
"System down, please try again in ten minutes," might be bad, but isnt it better than, "Here we are, welcome to amateur hour"?
Conversely, a less gold-plated online ordering system might actually be down, but the Web site might still be able to offer the customer access to an online catalog combined with a one-click facility for e-mail inquiries and a promise of next-day reply. Properly implemented, a system like this need not be labor-intensive: on average, it could easily cost much less than adding more nines to your 99.99…percent availability, and it could actually yield higher customer satisfaction than a system thats always up but doesnt actually answer customers questions.
Woody Allen famously told us that 80 percent of success is just showing up. Financial gurus can even put numbers on this principle: If you missed the stock markets ten best days between 1970 and 2000, you made 40 percent less total return over that period than those who were fully invested in a representative sample of stocks throughout that same time. Many industries are at least this narrowly focused: failure to be there for the customers on a few crucial days of the year can turn a good years profit into a loss.
The "Black Friday" nickname for the day after Thanksgiving denotes the shift from loss (red ink) to profit (black ink) that makes that day so vital to so many. Your own industry sector may have different critical days, and the heck of the thing is that you may not be able to predict them in advance: you just have to plan to show up, every day, or perhaps in the modern era I should say, every hour.
Make sure, though, that your definition of being there is based on the needs of the customer, not on measures that are better used to sell IT hardware than to meet your customers real-world desires and demands.