Thanks for returning to our ninth and final segment of Tech Service Today's technical buyer's guide series called Size Matters - Especially When Choosing A Network Rack. The goal of this series has been to educate IT professionals on the importance of every dimension of network racks and cabinets, and teach them best practices for determining their exact size requirements before ordering a new rack. Ultimately, this series will make you a more knowledgeable buyer so that you always purchase the product that meets your specific needs.
While accessories are not a size dimension of racks or cabinets, they are important items to include in your evaluation process - especially when considering a rack that offers proprietary accessories (like cable managers, fans, and specialty PDUs). Therefore, this last segment is dedicated to the optional items that IT professionals should consider carefully - but all too often don't think about - when shopping for a new cabinet or rack.
Part 9 - Accessorizing your new Rack or Cabinet
Whether you are shopping for a new 2-post rack, 4-post rack, or a rack-mount enclosure to house your networking equipment and servers, it is important to give serious forethought to the more important rack-mount accessories, meaning the optional accessories which are not typically included with new racks or cabinets. Among the most frequently forgotten, yet necessary components of any well designed rack-mount solution, are the Cable Managers.
Over my 25-year career in the IT industry, I have received thousands of rack design drawings from CIOs and other IT professionals who were completely confident that their plans had covered everything that would go into their racks...until I pointed out the absence of cables. Obviously this was chiefly because of how difficult it would be to incorporate cables into the drawings - even if there were Visio or AutoCAD stencils of cables available. But because the cables are out of sight, the products needed to organize and manage them are often forgotten.
Every piece of rack-mount equipment requires data cables to provide network connectivity, and power cables to run them (with the exception of passive devices like patch panels). If you fail to incorporate cable managers in your new rack plans, then you will probably end up with a rack similar to those featured every Friday in TST's IT Disaster Of The Week photo blog.
When shopping for a 2-post or 4-post open frame rack, you can usually find vertical cable managers that span the full height of the rack, sometimes referred to as vertical Cable Channels which are made specifically for use on those racks (or generic slotted duct raceways that are made to mount on most open frame racks). But because rack-mount enclosures are designed with side panels, that type of full-height cable channel is not an accessory commonly used with cabinets.
As such, you will need to consider using vertical cable management rings to organize your cables and prevent them from blocking access and visibility to the face of your equipment. To minimize the possibility of electromagnetic interference (EMI), I always recommend running cable rings down both of the rear rails of a cabinet, with all of the power cables being routed through the rings on one side while the data cables run down the rings on the opposite side.
If your new rack will house any high-port-count data equipment like patch panels and switches, a horizontal cable manager should at least be positioned directly above or below that equipment. But the ideal solution is to position smaller horizontal cable managers both above and below the equipment so that the cables connecting to the top-ports are routed through the cable manager situated above the equipment, and vice-versa. If cables from the top and bottom ports are both routed to a single cable manager positioned above or below the equipment, then it reduces your access to one row of cables and increases the potential for accidental disconnects.
One critical consideration to keep in mind when choosing vertical and horizontal cable managers for a cabinet is the impact they can have on your rail depth. For example, let's say you have chosen a cabinet that offers a maximum rail depth of 30-inches because your deepest piece of equipment to be mounted are several 28-inch deep servers. Additionally, your cabinet will also house several 48-port patch panels. Because of all the cables connecting to those patch panels, you have chosen some extra-deep horizontal cable managers that stick out 4-inches in front of the front rails. In order for you to be able to close the door to your cabinet (with those cable managers preventing you from doing so), you will need to adjust the front rails back about 3-4 inches. By doing so, you are reducing the maximum rail depth from 30-inches to around 26-27 inches. As such, you may no longer be able to mount your servers at all four corners.
BUYER'S TIP for Choosing the Right-Size Cable Managers
The biggest challenge most people face when trying to select cable managers is determining which size cable manager will accommodate all your cables. Fortunately, we can help. Using the cable dimensions below, do the math to calculate the minimum size of the cable rings/channels that you need for your cable managers. And always add room for growth (more cables to be added in the future).
CABLE TYPE DIAMETER
Category 5e 0.28”
Category 6 0.32”
Category 6a 0.34”
EXAMPLE: A cable manager with 3” rings will hold approximately 100 Cat5e Cables.
In addition to cable managers, there are a number of other rack accessories that should be considered before placing an order for a new cabinet or rack. For starters, are you planning to set up your racks or cabinets side-by-side in a row? Then you should ask the manufacturer for a Baying Kit (aka multi-cabinet Joining Kit) to ensure that they can be connected together properly.
If you are planning to mount your new rack or cabinet to the floor or a wall, then you will need the necessary hardware (screws, bolts) to accomplish that. I often hear IT professionals complain about the fact that rack manufacturers do not include this mounting hardware with their racks. While I understand their frustration, it is important to understand why the mounting hardware is not included. It is because of the countless types of walls and floors (concrete, drywall, raised floors, plywood, plaster, granite, marble, stone, wood, etc.) - all of which require different kinds of mounting hardware. So remember to make a trip to your local hardware store before you begin installing your new cabinet or rack.
In addition to purchasing the hardware needed to mount your new rack or cabinet to the wall or floor in your facility, you should also make sure you have an ample supply of equipment mounting hardware. While 12/24 or 10/32 mounting screws are often included with whatever rack-mount equipment you purchase - and sometimes with the racks themselves - they are easily lost. It is also important to note that most 4-post racks and cabinets being made these days feature M6 rails which have the large, square mounting holes. While the M6 holes are exactly what you need to mount most servers, your other rack-mount equipment was likely designed to mount on threaded rack rails (meaning smaller, round holes). To mount that equipment on M6 rails, you need M6 Cage nuts which effectively turn those square holes into round ones. Regardless of the type of rails you get with your new rack, always make sure you have a plentiful supply of the screws and/cage nuts needed to secure all your rackmount equipment.
The last type of rack accessories warranting serious exploration are Power Distribution Units (PDUs). Companies like APC and Tripp Lite have countless standalone and rack-mountable PDUs to choose from, as well as Uninterruptible Power Supplies (UPS). The simplest means for determining your PDU requirements is to start by counting the number of rack-mount devices that require power - remembering that devices with redundant power supplies will require two outlets.
Once you have calculated how many outlets you need, answer these questions:
1. Do you want an on/off switch on your PDU?
While a power switch allows you shut off power to all connected devices simultaneously, it also serves as a potential point of catastrophic failure because accidentally flipping the switch can take your entire network down.
2. Do you want a Basic, Metered, Monitored, Switched, or Dual-Circuit PDU?
To better understand the differences between each type, Tripp Lite offers a great overview of each.
3. Do you want the outlets/receptacles on the front or back of the PDU?
Regardless of whether you plan to mount a horizontal PDU or power strip on the front or rear rails, there are many reasons why some IT professionals prefer outlets on the front or back of their power strips. For example, power cables are thicker than data cables, and therefore have a lower allowable bend radius. That means they will stick out further than your data cables. If those power cables are on the front of your rackmount power strip/PDU, it could prevent a cabinet door from closing. Additionally, front-outlet power supplies require the data cables to be placed nearer to the data cables in your cabinet or rack, increasing the possibility of EMI. In these cases, a PDU with outlets on the back is a better choice.
4. Do you need Surge Protection on the power strip or PDU?
In most cases, you will not because your PDU will likely be plugged into a UPS. But if you are not using a UPS, then a PDU with built-in surge protection is a worthwhile investment.
5. Do the power plugs from every piece of rack-mount equipment match the type of outlets/ receptacles on the PDU?
APC offers a fantastic Rack PDU Selector tool to help you find a PDU with the right outlets and sufficient power to support all the devices you want to connect.
6. Do any of the power cords for your rack-mount equipment have the big power-block transformers on the plug end?
The big block transformers at the end of some power cords are a source of frustration for almost every IT professional because the outlets on most PDUs are spaced so closely together that the power bricks block access to the outlets on either side of the one into which they are plugged. If you have run into this situation, do not go out and purchase another PDU. Consider purchasing a short AC power extension cord/cable which can plug into your PDU without blocking adjacent outlets (with the transformer block plugging into the end of the power cord). gets plugged into the female end of the cable, thus restoring full access to every outlet on your PDU. Companies like C2G, Tripp Lite, and Black Box offer these power extension cables in lengths of 1-foot or less to keep this solution clean and neat.
Keep in mind that most manufacturers of rack-mount enclosures (cabinets) now offer server cabinets with built-in PDUs - usually situated off to the side of the vertical mounting rails or inside the back frame of the cabinet (beside the rear door). These non-traditional, "zero U" rack power supplies are increasing in popularity among IT professionals because they eliminate the need for PDUs to occupy the valuable space on their mounting rails.
Tech Tip #9 - Rack-Mount Accessories To Consider
Here is a summary of the rack-mountable accessory products that IT professionals should always evaluate and choose while they are selecting a new cabinet or rack.
- Vertical and Horizontal Cable Managers
- Cabinet & Rack Joining Kits and Hardware for Wall/Floor Mounting
- Equipment Mounting Hardware
- Power Distribution Units (PDUs)
- Rackmount Fan Trays and Filler Panels
- Patch Panels
- Ladder Rack
We hope you have benefited from the explanations and suggestions presented in this post, and every segment of our Size Matters - Especially When Choosing A Network Rack series.
To receive a copy of TST's complete Racks & Cabinets Buyer's Guide containing all the tips offered in this nine-part series, just fill out the Contact Us form below and write SEND ME THE GUIDE in the Message box.
DID YOU MISS EARLIER SEGMENTS OF THIS SERIES?
Not to worry! Here are links to our previous discussions about every dimension of racks and cabinets, the importance of each of these measurements, and tips for calculating your size requirements for each.
Internal Depth and Maximum Rail Depth
Door Types (on rack-mount enclosures/cabinets)
What's Included (or Not) With Your New Rack
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