Unix as a Second Language

Reducing your cable mess

It doesn't take many years for the cabling in a moderately sized server room to become a maintenance nightmare. Some racks I've worked with have become so full of network cabling and power cords that it is nearly impossible to reach inside and push a power switch, never mind insert a new network or console cable. Having gone through an exercise in pulling out hundreds of installed yet unused cabling in order to rearrange the contents of a series of computer racks, I can tell you from the perspective of hindsight that some basic rules for managing your cable plant can save you a lot of time in the long-run.

Rule one: Label, label, label! There is nothing more time-consuming and frustrating than having to manually trace one cable out of dozens all bundled together to figure out what the other end is plugged into. A scheme whereby each cable is labeled at both ends to indicate what it connects to can save you hours of time. If ultraviolet is plugged into port 11 on switch 4-4, the switch end of the cable should be labeled "ultraviolet" and the system end should be labeled "4-4:11". Better yet, both ends should be labeled with both pieces of information. If you have to move a cable out of the way for some reason, it will be easy to know where to plug it back in when you're done.

Some cable providers will be very happy to prepare cables for you with any type of labeling you want. You can also purchase a labeler for a modest fee. With my factory refurbished brother P-touch, I can print labels up to 1" in height and in four different colors (depending on the cartridge I use, of course), thus providing extremely useful documentation of my wiring.

Rule two: Use cables that are close to the length you need. If all you have are very long cables, you will end up with lots of long cables that get in your way when you're working in your racks or you will tie your cables into bundles to keep them neat, thereby making the job of tracing cables from one end to the other that much harder. This rule applies to power cables almost as much as network cables. If a system is plugging into a power strip that's one foot away, don't use the longest power cable you have on hand. Unfortunately, what you're going to have on hand are likely to be standard length cables, but you can get 1-3 foot cables for around $2-2.50.

It's also a good idea to categorize cables that you remove from racks for later reuse both by type (cat5, cat6, crossover, console) and approximate length. I have found a fast and easy way to measure cable lengths before I bundle them up and add them to my supply cabinet. The arm on my desk is four feet long. I hold up each cable and count off how many four-foot lengths it comprises end to end. I don't bother being too precise, but I won't end up grabbing a 16 foot cable sometime down the line when a 4 foot cable would do.

Rule three: Remove unused cables from time to time. I have quite a few pounds of cable in my office that was recently removed from racks in which it was strung but not connected to anything. When you remove or move a system, don't leave the old cables in the rack unless you're going to use them again sometime soon. It's surprising how much "dead" cabling can collect in a few years, making it increasingly difficult to make any changes at all.

Rule four: Use cable ties sparingly. It's a great idea to keep cables bundled and pulled aside, but if you tie the bundles too frequently, you make it very difficult for any cables in the bundle to be removed later.

Rule five: Consider using color-coded cables for your more critical systems or for certain types of systems. This will make it far easier to spot those cables when they are threaded between racks.