Network performance problems are among the most difficult network problems to track down and solve.
If a user simply can’t access the network, it usually doesn’t take long to figure out why: the cable is broken, a network card or hub is malfunctioning, the user doesn’t have permission to access the resource, and so on. After a little investigation, the problem usually reveals itself — you fix it, and move on to the next problem.
Unfortunately, performance problems are messier. Here are just a few of the reasons that network administrators hate performance problems:
Performance problems are difficult to quantify. Exactly how much slower is the network now than it was a week ago, a month ago, or even a year ago? Sometimes the network just feels slow, but you can’t quite define exactly how slow it really is.
Performance problems usually develop gradually. Sometimes a network slows down suddenly and drastically. More often, though, the network gradually gets slower, a little bit at a time, until one day the users notice that the network is slow.
Performance problems often go unreported. They gripe about the problem to each other around the water cooler, but they don’t formally contact you to let you know that their network seems 20 percent slower than usual. As long as they can still access the network, they just assume that the problem is temporary, or that it’s just their imaginations.
Many performance problems are intermittent. Sometimes a user calls you and complains that a certain network operation has become slower than molasses, and by the time you get to the user’s desk, the operation performs like a snap. Sometimes you can find a pattern to the intermittent behavior — say, it’s slower in the morning than in the afternoon, or it’s slow only while backups are running or while the printer is working. Other times, you can’t find a pattern. Sometimes, the operation is slow; sometimes, it isn’t.
Performance tuning is not an exact science. Improving performance sometimes involves educated guesswork. Will segmenting the network improve performance? Maybe. Will adding another 512 MB of RAM to the server improve performance? Well, hope springs eternal.
Thee solution to performance problems is sometimes a hard sell. If a user is unable to access the network due to a malfunctioning component, there’s usually not much question that the purchase of a replacement is justified. However, if the network is slow and you think you can fix it by offloading your server’s contents onto a separate server, you may have trouble selling management on the new purchase.