Wireing Question for Data Center

Question

I work in what I would consider to be a small/mid sized data center. We use two 6513 as the core/distribution for ~25 racks of servers.
My question comes in the way of cabling the servers to the core. Currently they are using long patch cords between the 6513 and each server. Well it’s a mess, functional but messy.
I'm trying to figure out the best way to clean up the mess and make it look professional.
Most people seem to suggest 2 different ways to accomplish this:
1) Install switches in each rack and run fiber from the core to the rack. Wire each server to the switch in the rack.
2) Install 24/48 port patch panels between the core area and the racks.
I'm wondering what people think of these ideas and if there are any other suggested ways of accomplishing this?
Andy

Answer 1

Hi Andy,
Here's something that we used to do where I worked:
We had 6509's with three/four 48 port blades servicing between 150 and 200 phones roughly. I had four total switches, one on each of four floors. So this would be roughly similar to your DC environment, only we're servicing longer horizontal runs and phones, not servers -- but the idea is the same (i.e. high density cabling issues).
Lord knows that when you're plugging in 48 cables into one of those blades, it can get pretty crowded. And since we don't yet know how to alter the laws of physics that determine space requirements, we have to search for alternatives.
Back to my environment: On three of the four floors, we just wired straight from the patch panel (that ran to floor locations) to the switch. Quite a mess when you're running in 48 cables to one blade! However, this is traditional and this is what we did. My cabling guy (very smart fella) suggested something else. At the time I was too chicken to do it on the other floors, but I did agree to try it on one floor. Here's what we did:
He ran Cat5 (at the time, that was standard) connections in 48 cable bunches from an adjacent wall into the switch. They had RJ-45 connections so that they could plug in, and they were all nice and neat. On the other end, they plugged in to a series of punch down blocks (kind of like you see in a phone room for telephone structured cabling). These, in turn, were cross connected to floor locations on another punch down block that went to the floor locations. Now, whenever we wanted to make a connection live, we simply had to connect the correct CAT5 jumper wire from one punch down block to the other. You never touch the actual ports in the switch. They just stay where they are. All alterations are done on the punch down blocks. This keeps things nice and neat and there's no fiddling with cables in the switch area. Any time you need to put in a new blade, you just harness up 48 more cables (we called them pigtails) and put them in the new blade.
NOTE: You could do the exact same thing with patch panels instead of punch down blocks, but with higher densities, it's a bit easier to use the blocks and takes up much less space.
ADVANTAGES:
* Very neat cable design at the switch side.
* Never have to squeeze patch cables in and out.
* Easy to trace cables (but just better to document them and you'll never have to trace them).
* Makes moves, adds, and changes (particularly adds) very easy.
DISADVANTAGES:
* Not sure that you can do it with CAT6.
* You have to get a punch down tool and actually punch cables (not too bad though after you do a few).
* You need to make sure that you don't deprecate the rating on the cable by improperly terminating it (i.e. insufficient twists)
Anyway, I haven't had a need to do this in a while and I no longer work at the same place, but my biggest concern would be if that meets with the CAT6 spec. Not sure about that, but your cabling person could probably tell you.
I'm not a big fan of decentralizing the switches to remote locations. It can become cumbersome and difficult to manage if you end up with a lot of them. Also, it doesn't scale well and can end up with port waste (i.e. you have 24 servers in one cabinet on one switch and then along comes 25; you now have to buy another 12 or 24 port switch to service the need with either 11/23 ports going to waste -- not good).
Good luck. Let us know how you make out. I'd be glad to go in to more detail if the above isn't explained well enough.
Regards,
Dave