We have a 24U rack in our lab and I'm going to completely redesign it during the next weeks due to the scheduled big hardware upgrade.
I have a couple of the questions about the layout of the server components:
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UPSes. At this moment all UPSes (we use non-rackmount) are installed on the shelf near the top of the rack. Some people suggest to always put UPSes on the bottom but I'm just afraid what if the nearest server fall on them? I've never had a problem when server is falling down but never say never. One story is when it just fall on the rack stand, another story is when it crash an equipment.
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Switches. Usually people suggest to put them on the top of the rack, but I can see the only practical reason doing this: when I open rackmount KVM, it makes the switch front panel inaccessible, that's good because it usually shouldn't make inaccessible any other equipment except a switch. On the other hand, all cables are going from the bottom and you need to stretch them thru the whole rack. If you change the cables frequently (in the lab/development setup you do), it could be a headache.
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Patch panels – to use or not to use. And if use, how? Usually people connect all incoming cables to the patch panel then use panel RJ sockets to route them inside a rack, I agree it's useful for the large installations. But we actually have about 8 cables going in/out, why don't connect it directly to the switches?
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Use a short cables just to connect an equipment or make them longer to allow getting a servers out without a disconnect? A first choice will never cause a cable hell in the future, but it doesn't allow to get a servers out without powering them off. Remember, this is for the development lab, but putting some of the equipment offline (i.e. SAN) may cause the whole lab to go down up to the hour.
Probably enough for one question. Thanks for all answers.
Best Answer
UPS location
Bottom. Really. All that lead acid out-weighs a solid steel server any day. You want that in the bottom. Unlike servers, it'll get pulled out next to never. It'll provide stability in the bottom of the rack. Also by not putting all that weight at the top, your rack is less likely to act like a metronome in the case of some heavy rocking.
Switches vs. Patch Panels
Depends on your config, but for a 24U I'd lean towards switches. Or if possible, external patch-panels that then feed cables into your rack.
Cable Management Arms, or, what length of cable do you need
For 1U servers, I've stopped using the arms. I'll undress the back of the server if I need to pull it out (label your cables!). For 2U servers I have no firm opinion, but for larger server the arm makes sense.