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I've ordered some rack hardware from Dell. A 42U rack, a 3U EqualLogic SAN, two 1U PowerConnect 5424 switches, three 1U PowerEdge servers, and some other stuff such as a tapedrive, firewall, UPS, etc.

Since I have little experience with racks I wonder why the switches have their ports on the front of the rack, while all the devices that connect to it (SAN, servers, tape, firewall) have their ethernet ports on the back.

My assumption is that is makes it easy to plug/unplug cables, and to watch the blinkenlights. It does make the cable management a bit more awkward though, since I'll have to feed all the cables from the back of the rack to the switch ports on the front, either via the side of the rack or by leaving some vertical space between the devices.

Why is this, and what is a good way to manage the cables?

Any tips or pics on how to layout a rack with such diverse hardware in it?

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5 Answers 5

up vote 17 down vote accepted

Because typically, networking gear goes into its own racks, and servers go into their own racks. The network rack will often have patch panels in it, also on the front, so that the cables all just go into cable management - on the side of the racks and/or across the front of the racks.

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Switches need to be reverse mounted (ie, their ports should face the same way that the server ports do, toward the back of the rack).

Also, maybe you can get some use from this: http://www.standalone-sysadmin.com/blog/2008/06/howto-racks-and-rackmounting/

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that's an interesting link, although apparently the author doesn't understand how to use cable management arms –  Jim B Jan 27 '10 at 14:50
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I tend to agree with mfinni that the reason is that traditionally servers were patched to network switches, it's not like switches have their fans reversed, they still blow the same way as servers so reversing them can cause heat-spots. Sorry to be negative for once matt, you know I still love your posts don't you ;) –  Chopper3 Jan 27 '10 at 14:53
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@Chopper3, I noticed some switches allow you to reverse the airflow direction via the firmware. Most likely exactly for that reason. –  Martijn Heemels Jan 27 '10 at 15:03
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@Jim B - the author doesn't care much for cable arms :-) But that's another discussion –  Matt Simmons Jan 27 '10 at 15:26
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@Chopper3 - yeah, we're still cool ;-) –  Matt Simmons Jan 27 '10 at 15:27

You would normally have your switches matched up with patch panels, so wherever your patch panels are, your switches will be near. When plugging in ports, it is useful to see the status LED as you plug it in to confirm connection. They also stick the serial management port in the front also for easy access. They stick the switch daisy chain connections (at least older ones always seem to do) and power/redundant power on the back as those do not get accessed often.

Easiest way to manage is to get the rack wire management plates and stick them between every switch or every other switch to help keep cables in order. A great example of this gone bad is the server fault error page. I remember I got to clean up a mess like that once at an old job. Took hours to install new cable and patch panel organization after years of neglect after each technician, but it was much easier to manage after that point.

Also, if you got a few bucks, buy lots of various lengths of cables to keep your cable management sanity. Using 10ft cables for every port that is 12 inches away to 9 ft away just turns into lots of extra cable hanging and filling up wire management space.

I am not endorsing belkin products, but these are good examples of some of the different styles available. http://shopping.yahoo.com/s:More%20Computer%20Accessories:3141-Accessory%20Type=Rack%20cable%20management%20kit%20%28horizontal%29:4168-Brand=Belkin

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This is a good idea, if you've got a lot of of matching patch panels and switch ports, because then you can do cool things like this: neatpatch.com –  Matt Simmons Jan 27 '10 at 14:20
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@Matt: NeatPatch is interesting. We put 1U in between switch/panel and use 1 foot patch cables without the need for the loop and fingers. –  jscott Jan 27 '10 at 14:48
    
@Matt: That is a really cool solution. That looks very clean/professional. –  Troggy Jan 27 '10 at 14:51
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We've used NeatPatch at several Customer sites and love it. It makes for a very setup. I hope those guys, along with the guys who thought up quick-release rack screws (rackrelease.com/QuickReleaseRackScrewsExtendedRoundCap.asp) make boatloads of money... –  Evan Anderson Jan 27 '10 at 15:44
    
I also love the neatpatch stuff. Recently however I've gotten customers that don't believe in patch panels- they'd rather just run cables all over the place. Even better- they refuse to make cables but will only buy them- which will guarantee spaghetti wiring. I hadn't heard of rackrelease. Great Link! –  Jim B Jan 27 '10 at 23:33

This is an old post, but the "why" never was answered. I just hate dangling questions ;-)

The reason is most environments (think business office rather than server closet) use switch ports primarily connected to patch pannels. These, of course, run to office / cubes. Very often all wall ports in a building are not live, but will be connected based on need. By having both the switch ports and the patch panel ports facing front, making changes as people move is easier than reaching into the back of the rack.

The same holds true for large data centers, where primary switches will be centralized with distribution out to individual servers or network equipment housed in racks throughout facility. Again, easier to change as needed by having everything front facing.

In server closets, individual or small cluster of racks, as has already been mentioned, people will sometimes choose to mount the equipment reversed. This is fully supported by the manufacturers who generally place mounting holes for ears both front and back.

I have also seen the server/equipment switches mounted reverse with distribution mounted standard.

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Um, my (accepted) answer does say : "networking gear goes into its own racks, and servers go into their own racks. The network rack will often have patch panels in it, also on the front". So I'm not sure why you say this question has been unanswered. –  mfinni Aug 20 '12 at 17:59

We place all of our switches and firewalls facing the back of the rack. It cuts down on the blinking lights up front, but makes cable management easier. I never really thought about why they are like this, but I would love to know why if anyone else can add some insight.

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I suspect it's because they hearken back to the days of telcom racks that were only 2 post, so there was only a "front". Plus there's not enough hardware in there to necessitate a full-length chassis, and reverse mounting them works fine, with the exception of the "how do I run my power cable" thing –  Matt Simmons Jan 27 '10 at 14:16
    
Yes, generally I've also seen network switches mounted to the top/back of the rack. –  robbyt Jun 11 '12 at 4:56

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