How difficult is it to manage and track different levels of availability for different systems?
Some people choose to outsource the hosting of their highest-availability applications to an ASP or MSP (managed service provider). They can then group all the lower-availability applications on their in-house servers. But you can’t make different in-house applications wildly different, unless you’re willing to invest in separate servers, hot-spare standbys, UPSes and so on. How do costs play in the equation? Is it safe to assume that it gets more expensive as the number of nines goes up? It generally gets more expensive, depending on your environment. But going from four to five nines could be a 10% or a 400% increase. It depends on what you’ve got. How do you figure out “failure acceptability” — that it’s okay for an application to be down for a particular amount of time? Who needs to be part of that decision? You need to look at percentage of downtime versus uptime and how long the downtime lasts. EBay may have 100 outages/month for a half-minute and no one notices. But if they hav
