Cables on a closed rack

Question

I've just spent the last few days building my first server rack. It will be a significant upgrade to our current mess. I was asked to buy and install one and so I did. I was not completely aware of the distinction between a closed and open rack, though I did compare them and chose a closed one due to it looking more 'fully featured' than the more bare skeleton looking ones.

I've already received some criticism from third parties about my intention to put cabling into a closed rack. "That's not a rack, that's a cabinet" they say. (It is a 4-post 42U closed rack (cabinet/enclosure).) They think I should use a second open rack and put all the networking in the second rack instead of this one. We will have a second open rack anyway, which will be holding some fibre optics that will be connecting to our main ethernet network.

My question is: is it such a big deal to put cabling into a closed rack? Is it such a big deal to have a closed instead of open rack if security is not that critical? And maybe related: does it make more sense to put the fibre and ethernet network in one rack, and then servers and hardware in a second, or maybe to put the fibre stuff in one, and ethernet and servers in the second (I personally feel like I want to keep the fibre stuff separate from the ethernet stuff), or maybe it doesn't necessarily matter?

Answer 1

My question is: is it such a big deal to put cabling into a closed rack?

No. It can make working on the cabling more difficult and add time (i.e. labor costs) to the work, but I have seen this done well plenty of times. Of course, many organizations choose to use top of rack switches or extenders rather than cabling.

Is it such a big deal to have a closed instead of open rack if security is not that critical?

This is entirely dependent on your situation and the goals that are most important to the organization.. There are other reasons to use cabinets as opposed to free standing racks.

For instance, many cabinets provide for ways to provide 0U power solutions like PDUs that easily mount vertically out of the way. Or cooling, sometimes it is easier to create hot/cold aisle separation using cabinets or you could be planning on implementing cooling directly into the cabinets to increase the cooling efficiency.

Some people also find cabinets a better as it helps to prevent inadvertent cable/power disconnects when people are working in neighboring racks. If someone can't be "brushing" up against cables, there is less chance for something to be disconnected.

The reasons to use a cabinet besides security are varied. Of course, there are reasons to use free standing racks as well.

And maybe related: does it make more sense to put the fibre and ethernet network in one rack, and then servers and hardware in a second, or maybe to put the fibre stuff in one, and ethernet and servers in the second (I personally feel like I want to keep the fibre stuff separate from the ethernet stuff), or maybe it doesn't necessarily matter?

Again, this will highly depend on your particular situation. I have seen all of the above used at different points for different reasons. You need to decide what makes the most sense for your organization.

Answer 2

Some people are fussy about terminology, but I've usually heard "rack" for place to put 19-inch mounted equipment and shelves, and usually "cabinet" when it has doors. If it's both then it's a matter of emphasis or local custom.

How you organise your servers and patching and routers is up to you and depends a lot on what you've got and what changes are likely. How open or closed they are depends on security, money, thermal and noise.

For example, many servers are rather deep; most networking equipment is not.

For networking things, especially patch panels, I normally like to have the vertical rails quite far from the front, so the patch cables have room when the door is closed. I don't really distinguish between fibre and copper cabling, just how far it's going. Fibre obviously needs more room though.

I've often found it beneficial if the patch panels are all in one rack as they're going to be a pig to move. I like sides on racks and proper routing for inter-rack cabling. In a couple installations I put all power and interrack cabling out the top so not a single cable touched the floor -- was a basement and yes when there was flooding we didn't much care. Big wheels on the bottom (with brakes) will be a lifesaver when, eventually, they have to move. Finally, don't get racks taller than your doors!

Just some thoughts.

EDIT: I can also hugely recommend UPS-per-rack (at the bottom) and inter-rack patch (at the top). With good wheels you can keep your systems up during a move if you want to.

Answer 3

In my opinion this is really not a problem of closed or open rack but more a question of :

• How long/large is the rack
• How you manage cabling and equipment positioning.

I used to work for a datacenter and I always provided following advices :

• use closed rack (mainly for security reasons)

• If you don't have any area issue, use a long and large rack, those designed for network equipments are the best ones. This allow easy access and avoid cabling issue.

• put all cabling at the back of the rack. This mean that if you have a switch, it's a better option to put the switch at the back. You can find switches with reverse airflow (even without, most enterprise switches support quite high temperature and can be safely put in the hot aisle - with adequate supervision)

• Use vertical PDU and really short power cable

• Use ethernet cable and optical fiber of the exact length. Having a set of (0.5m, 1m,1.5m,2m,2.5m,3m) is generally a good start. Don't rely on color of cables, i've see lot of people (un)plugging the wrong cable just because they thinked that there was only 1 pink cable in the mess.

• Don't mix Power cable with ethernet cables (even if I never noticed any EMC issue on my own)

• Don't mix Optical cables with ethernet cables or power cable. Optical cables are quite fragile and it's quite common to damage them trying to quickly plug back the ### pink cable which was not supposed to be removed. At least use snag-less RJ45 connectors which avoid the fiber to be trapped with the release clip of the RJ-45 connector.

• Avoid the cable to go out of the cabinet / rack. using scratch tape help a lot

• Don't hide anything, you'll regret it.