48

We've all seen good and bad examples of cable management.

  • What are objective, measurable requirements that can be used in a policy to maintain cabling order in the rack/server room/data center?

I'm not looking for "Don't do spaghetti wiring!" but practical, objectively measurable policy that can be readily explained, followed, and inspected for whether it passes or fails the requirements in the policy.

Please avoid, "Don't do x, y, or z" - instead re-form the requirement as a "Do A, B, and C" where following the second requirement will eliminate the problems explained in the first requirement.

HopelessN00b
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Adam Davis
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7 Answers7

48

Use cables as close to the correct length as possible.

Spare cable should be coiled away from the concentrator - so spare power cable gets coiled next to the machine, not the powerstrip, and spare network cable next to the machine, not the hub.

Don't be stingy with cable ties, be they zip ties or velcro pulls. When in doubt, use an extra, and don't hesitate to trash old ones.

Machines should still be removable once unplugged, which means run your cables vertically down the edges of the rack, not the middle.

Only run cross-rack in one place (probably the top or bottom of the rack), and run as little cross-rack as possible.

Color coding is good, but when troubleshooting, what is trumps what's supposed to be.

Fix it all now. 'Later' never comes. Corollary: everything should always be perfect before you leave - or you have concrete plans to come back and fix it.

Label cable ends with abstractions: numbers, letters, whatever. Don't bother with 'firewall', 'external', etc - they'll get moved and re-used and the labels will be wrong; better to keep the labels an extension of the 'color' so they can be easily reused without having to be relabeled.

A lot of this is from old telco practice - you think we manage a lot of cables, you should look inside a real telco crossconnect sometime - well, but don't because they're often spaghetti.

pjz
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    +1 for the cable labeling - label both ends with a unique serial number (or combination of letters/numbers). One can even store this info in the database with all the other equipment and connection info. – Adam Davis Apr 30 '09 at 19:26
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    Zip ties should never be used with Ethernet cable, as it will cause damage to the twists inside the cable. This causes increased interference, which can cause problems, especially as you go up through Gbit speed rated cable. – Dominic Eidson Apr 30 '09 at 19:50
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    Followup to that - use velcro cable ties. They hold things well in place, and are easy to manipulate should you have to add/remove cable to a bundle. – Dominic Eidson Apr 30 '09 at 19:51
  • @Dominic - plus you don't end up with a ton of zip tie trash on the floor, or worse in the subfloor. – Adam Davis Apr 30 '09 at 20:04
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    When ever you feel the need to use a ziptie, remember this simple rule: For every ziptie used, you will remove two. – Joseph Kern Jun 16 '09 at 13:24
  • @Joseph, +1 thats a great rule – faultyserver Nov 05 '09 at 01:12
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Always, always, always take the time to strip out those cables you aren't using anymore. Pull it all the way out of the rack/patch panel, coil it up and put it away (or throw it away, as appropriate).

And when you're getting rid of dodgy cables. Cut off one or both ends. They will come back and haunt you if you don't.

quux
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8

No zip ties. Velcro.

Consistent color coding.

Label both ends of cables, always. Even if you have serial numbers. It's cheaper to pay a cabling guy for a whole year than to have one cable-related mistake.

Never allow temporary setups unless it is an emergency. They never are temporary.

Using the exact correct length is pretty but is terrible to maintain. But extra length is its own pain. Tough decision to make.

Don't leave unused cables laying around! I saw a 30 year old data center with unused cables just cut and dropped under the raised floor. Really.

carlito
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8

Be consistent!!!!

I don't care what colors you use for what, but always use the same ones. I don't care if the vertical run between units is on the right or the left, but always put it on the same side. I think you get the idea.

If it doesn't look neat, it isn't. Pick some pattern, some system and follow it.

A touch of OCD doesn't hurt. (apology in advance to any one from the Politically Correct crowd who want to flame me for make fun of being OCD).

Jim C
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6

Please don't zip-tie things together super tight. If you really must use zip-ties, keep them loose. Makes it a huge pain to move cables if everything's all tied together.

Brian Knoblauch
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5

A good start is colors. I'm not sure there's a convention, but you could use something like:

  • Blue for switch<-->computer.
  • Yellow for switch<-->switch.
  • Red for Lights out/power
  • Orange is always FC, of course...
Jared Oberhaus
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    Don't forget to call out internal (firewalled) and external connections, among other colors... – Adam Davis Apr 30 '09 at 19:08
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    I'd be interested to know if anybody has a standard. I've personally been using blue for workstations, yellow between switches, and red for the router. Basically in order of danger level if you unplug. – Scott May 28 '09 at 23:26
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You know, most shops don't like to use them, but Telcordia publishes standards for this sort of thing. They are pretty heavy-weight, but they exist so that shared shops can say "everything must be cabled according to Telcordia-blah-blah and everyone know what that means.

Unfortunately you have to pay for them, but these look like a couple of good places to start if you really want some backing for your standards:

  • TIA-568-C.0 Generic Telecommunications Cabling for Customer Premises
  • TIA-568-C.1 Commercial Building Telecommunications Cabling Standard
slm
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jj33
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    Usually for these kinds of professional standards, there's a lightweight summary online somewhere that outlines the basic and most important/prominent concepts. Is there anything like that for these? – Adam Davis Apr 30 '09 at 19:53
  • The following seems to give a decent quick overview: http://www.siemon.com/us/standards/09-06-10-update-568-c.asp – Scott Jun 10 '11 at 21:55