A rchive Date
[ 08-12-2000 ]
Category
[ Information Technologies ]
sub-Categoy
[ Networking ]
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[http://www.techrepublic.com/article.jhtml?id=r00320001115det02.htm
Use half splitting to solve difficult problems
Nov 15, 2000
Mike Sullivan
E-Mail
Part one of this series discussed troubleshooting basics. Part two outlined the practice of troubleshooting from the general to the specific. Part three addressed the methodologies used to narrow the scope of your analysis. In this article, the final part of the super geek series, I'm heading into the deep end of the troubleshooting pool. I'm going to share my secrets for troubleshooting the really tough problems, the ones that leave mere mortal geeks scratching their heads and wondering what they've missed. Learn how you can use the technique of half splitting to save your sanity when troubleshooting a difficult problem.
Start with documentation
When you are dealing with a relatively complex system, it helps to have a system diagram that shows the system components and how they relate to one another. That's right, I'm talking about documentation! It doesn't have to be anything complex, a simple drawing like the one shown in Figure A will usually work just fine. The important part is that it identifies all of the system's components.
| Figure A |
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| This took me about three minutes to create using Microsoft Visio 2000. |
The half-splitting method
With your documentation in hand and a tough problem on the table, it's time to start isolating the problem. The most effective method of isolating a problem is called half splitting. Here's how it works.
Using the system diagram in Figure A, let's assume that Desktop 2 is not able to print to the printer. You've already gathered the symptoms and checked for high probability causes (correct driver, printer is online, network connectivity, and so on). It's time to start eliminating components as possible causes. The list of possible causes for our hypothetical problem consists of six components:
- Desktop 2
- LAN 1
- Router
- LAN 2
- Server
- Printer
Create a system flow diagram
First, label each component A through F, respectively. Then create a system flow diagram that shows the flow of output between each component (see Figure B).
| Figure B |
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| This system flow diagram indicates that the output of A feeds the input of B, which then feeds the input to C and so on. |
Start in the middle and work your way out
Next, look at the output of C and determine if it is good or bad. Let's assume that the output of component C is good. You can, therefore, scratch A, B, and C off of your list of possible causes. Now, split your list again. Look at the output of E. If it's bad, you know that it or D is the problem. If it's good, you know that F is the problem.
While this may not seem like much of a time saver for this particular problem, imagine troubleshooting a system with 50 or 100 different components. When working on a system this large, the half-splitting method can dramatically reduce downtime
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