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We are thinking of getting a switch for our data center that blows air from the ports to the power plugs. However, we use a hot-aisle and cold-aisle layout. Our other switches blow in the opposite direction. In order to avoid fishing cables through the rack, I was thinking of purchasing two patch panels. One patch panel would face the hot aisle and the other would face the cold aisle. The switch's ports would face the cold aisle. Port 1 on one patch panel would connect to Port 1 on the other; Port 2 would connect to Port 2, and so on. Then, we would use short jumper cables from the patch panel to the switch in the cold aisle. In the hot aisle, we would run cables from the back of the servers to the patch panel in the hot aisle. What do you folks think? Is this a silly or bizarre way to do things or is it probably our best bet to keep the cabling tidy and manageable? If not, is there a better way? Thanks.

  • You would be adding impedance mismatches and more untwisting of the pairs that increases crosstalk. You will probably fail the cable category test suite and introduce problems. Modern network protocols require much more than simple electrical connectivity. – Ron Maupin Apr 15 at 12:50
  • Hello and welcome. Can I ask how fast the interfaces are running and how long are the patch cables? (Ie, without your proposed scheme?) – jonathanjo Apr 15 at 16:46
  • @jonathanjo: Hi. The ports all run at 1 Gbps. The racks are 42 U high. The switch is located at RU 40. The lowest server in the rack is at 1 U and the highest is at 34 U. So, the cables range in length from about 1.5 feet to about 6.5 feet in length. Thanks. – user1177071 Apr 16 at 2:19
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With gigabit, I'd definitely suggest you stick with something purely mechanical for cable management. Good patch panels and interconnects are more expensive than you might think, and it sounds like you have quite a few racks. Even if they are highest quality, from a failure rate point of view, you're replacing 1 cable, 2 crimps, 2 RJ-45 matings with 3 cables, 4 crimps, 2 punchdowns and 4 RJ-45 matings, on every ethernet connection.

You might consider custom laser-cut plastic cable guides, which are easily made by your local laser-cutter shop, and which can be arranged to exactly suit your cable layout. I've no idea your details of course, but I've made things like this for similar problems:

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The better way would be to purchase switches that blow in the good direction.

Otherwise we cannot really answer this because it really depends on your constraints.

Your solution is not silly, but the major drawback is that it takes 1U which could be useful for something else. If you have plenty of space in your rack and you are sure you will never need that U, then, fine.

However there may be two linked issues:

  • financially: you definitively want your patch panels to be tested to be sure they are compliant and this has a non trivial cost. This is to be compared with the cost of using the correct switch in the first place.
  • practically: despite the fact the standards do not have a minimal length, not all testing equipment can reliably test cables that are too short. That means you could have to fold in your rack more cable length that strictly needed, and that could be impracticable.

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