Cable Management For Dummies?

November 14, 2007 11:36 AM

Where can I find a simple tutorial on structured cabling?

I am a software engineer that has recently started working on my team's build servers. The build servers are in a rack with a very messy blob of cables hanging off the back of the rack. Since I've had to start fiddling with the cables, I decided to take on the task of making the cables "prettier."

This leads me to my question: where can I find a tutorial on structured cabling? My Google searches come up with stores that sell cable management hardware. I'm looking for something that looks like this:

Materials: 
1. infinity meters of velcro ties

Procedure:
1. Do this
2. ???
3. Easy cables!

Some more details: we have 2 or 3 cat-5 cables going to each of the 10 or 12 machines (thankfully, they are currently color coded), power cables running to PDUs, and a few servers need to be run off of a UPS.

posted by yellowbkpk to computers & internet (5 comments total)

I don't know of any tutorials, but always just use the following rules of thumb:

Use velcro ( especially in dev environments. or else you'll be cutting a lot of plastic. )

Color code wires for purpose where possible. ( And then document the scheme somewhere! )

Label, label, and label everything. ( usually at both terminating points if they're non-obvious ).

Make as much use of raised floor tiles as you can if you have them. These are usually good for longer runs.

Look into rack-mounted power strips if you don't already have them.

You're already doing the first two, so in addition to the other few this Slashdot discussion may give you some more pointers.
posted by zap rowsdower at 12:14 PM on November 14, 2007

The biggest organization/access problems I've encountered with cabling relate mostly to improper lengths of cable.

Often, you may need a three foot run, but only have foot-long and five foot cables. If you're mess mainly involves networking cables, try this:

• buy a few spools of the appropriate cable (cat 5, 5e or 6) in varying colors. But a few crimpers, and couple bags of RJ45 connectors and cable boots (don't cheap out and skip the cable boots - they make cables much easier to deal with)
• create a color to purpose scheme, document it, and stick to it.
• Build cables to the lengths you need.
• Use cable looms and velcro to snug cables together where appropriate.

Alternatively, if you're real good at planning, sketch out your hardware layout and figure out exactly the length and quantity of cables you need, and then order them from a reputable cable dealer. Buy more cables than need. Seriously. Use a color coding scheme to organize cables, and use looms and velcro.

It's a nice rule of thumb to make all of your shortest connections first - of course this will vary from setup to setup.
posted by terpia at 3:02 PM on November 14, 2007

Messy blobs of cabling have usually got that way by accretion of random lengths of cable over time. It doesn't actually matter much what you do today, since your beautiful color coded carefully measured cabling runs will turn back into random rats' nests within a year once you stop being responsible for them. Cable mess is like dust bunnies - it just grows when nobody is looking at it, and needs periodic cleaning up.

There is no system you can put in place that's guaranteed to keep working when you walk away from it. So, the best thing you can do is tidy up as best you can now, and arrange for the inevitable rat's nest to be easier for the next victim to understand.

If you're making up your own cables, color code them by length, using the EIA E6 resistor value series to generate the lengths:

10" blue
15" green
22" red
33" orange
47" yellow
68" grey
100" blue
150" green
220" red

and so on. Color coding by purpose is a lovely idea in theory, but the coding manual will be lost and/or ignored.

Make up twice as many of each length of cable as you currently need, and leave the unused ones in a cardboard box behind the rack. You can just throw them all in together, as the difference between a cable of a given color and one ten times as long is immediately obvious, and the colors sort out the rest.

My personal preference is not to use cable ties at all, since they make it harder to figure out which cables actually end up where. Make your connections using the shortest cable that will reach without being stretched tight, and as terpia says, put the shortest cables in place first.

If you're running multiple long cables, between two distant locations, use a Sharpie to make a patterns of rings around the cables near their ends, so you can easily match the ends up when you need to. Don't bother trying to make readable labels that say where things are supposed to go, since those will degrade and/or fall off and/or go out of date as the cabling inevitably gets rearranged. Matching ring patterns continue to work regardless of how the cables are used.

The result won't look terribly structured, but you will be amazed how easy it is to figure out where everything goes.
posted by flabdablet at 5:11 PM on November 14, 2007

Good responses above. I think color coding by purpose is better than length, though it depends on your environment. Definitely second the labeling suggestion (get a good labeler that will do serialization etc., the Brady TLS2200 is a good choice, though expensive). I disagree with the last poster about never labeling cables, but it is important to decide to what degree you are able to keep them out of date, and to NOT use labels at all if you can't keep them up to date. I'd say at least label what switchport the cable goes to if that's not going to change. We used to have the cables come out of the cable management slot next to the rack U that the cable was for, so it was obvious where the cable was supposed to go.

Building in cable management is great if you have the luxury; if not, you really should try and fit some into the existing space. Making cables to order will make things neater, but may take a while, especially at first.

Buy lots of extra stuff, look a lot at what other people do (both in your facility, if there are other customers there, and in photographs), prototype everything, and you'll start to get an idea of how things will work well in your environment. Everyone's environment is slightly different, so I don't know if you'll find a tutorial as detailed as what you're looking for.

I have some general suggestions in slides for a talk I gave at:
http://veggiechinese.net/data_center_management/

There is an audio recording of the talk somewhere too; I don't have a copy of the video yet.
posted by PandaMcBoof at 11:40 PM on November 14, 2007

I work in a data center and there are as many ways to run and dress wire as there are customers. Neatness counts, but labeling counts for more.

When I worked for a telco and we ran hundreds of miles of wire, everything was tied together in neat bundles and then tied to a support structure. When you make your own cables to length make sure to give yourself some slack, you don't save money saving wire. Every termination had a small loop of slack so you could move the wire out of the way when you needed to see what was underneath.

Dressing cable is often not as simple as you would think because it is an interactive process with what has gone before and what is expected to come in the future. But running the wire through an open channel along the edge of the cabinet is a definite plus. Don't enclose wire if you can avoid it.

All by way of discourse. You will surely find a way that works best for your installation.
posted by ptm at 5:12 AM on November 15, 2007