Nothing is particularly hard if you divide it into small jobs.
Troubleshooting is a series of steps that focuses on and eliminates possibilities within a larger, unknown problem. I could write a whole book on troubleshooting, but in this chapter, I try to cover everything you need to know about how to locate and resolve common problems in your storage area network (SAN) environment. Read this chapter for every kind of problem, from the initial "Now why doesn't this work?" to the sudden "Whoa, what the heck just happened?" to my personal favorite: "Hey, do you smell smoke?"
Murphy's Law states that anything that can go wrong will go wrong, so being prepared and understanding what can happen and how to fix it will go a long way toward keeping your SAN healthy and operational — and you employed and sane.
Troubleshooting is basic problem solving. First, you have to know what the right setup looks like. When you have that knowledge under your belt, recognizing what's wrong is easy.
The key to avoiding having to troubleshoot, of course, is doing things right the first time. Unfortunately, to err is human. Mistakes happen. Don't let screaming users and deadlines rush you when you're making changes in your SAN. Because many things are tied together in the system, you can affect one application over there when you pull a cable over here. Be careful.
Understand what you're about to do before you do it, and keep your documentation ...