Size Matters – Especially When Choosing A Network Rack (Part 1 - Internal Height)

Cabling Tim Sauer Oct 31, 2017
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Guess what guys (and gals)? When it comes to choosing the right network equipment rack or server cabinet, Size Really Does Matter.

While many IT professionals think they know how to order the right-size rack for their servers and equipment, you would be shocked to learn how many racks get returned after being purchased because the end-user learned that it did not meet all of their needs.

When you consider how pricey it is to return-ship a full-size cabinet or rack via motor freight carriers, choosing the wrong rack can be a costly mistake.  The good news is that, with a little bit of guidance, every IT professional can learn to choose the rack or cabinet that absolutely meets their current and future needs.

The purpose of this blog series is educate IT professionals on the importance of every dimension of a rack or cabinet, and explain why each measurement must be evaluated before deciding on the product you purchase. Contrary to what many IT specialist think, you need to look at every dimension.

Each post in this series will focus on one internal or external rack dimension, and provide tips for ensuring it meets your needs. 
And at the end of this series, you can download our complete guide, Size Matters - How To Choose the Right Network Rack or Cabinet. So be sure to Subscribe to our Blog Post emails (using the fields on the right) so you learn the importance of every rack dimension, and gain access to our helpful Guide that proves once again, Size Matters.

Part 1 - Internal Height (U)

The next segment of this series will focus on the External height of racks and cabinets, and the considerations that must be weighed prior to choosing one.  But this first segment focuses on the Internal Height.

The general HEIGHT of a cabinet or rack is typically specified in Rack Units, which represent the maximum amount of rack-mountable space for your network equipment and servers.

A “Rack Unit” is a common increment of equipment space height as defined by EIA 310. It is a unit of measure used to describe the height of a server, network switch, or similar device in relation to the rails of the rack in which it gets mounted, as well as the maximum equipment racking capacity of cabinets & racks. Rack Units are abbreviated as “U”.

One rack unit (1U) equals 1.75" (4.4 cm) of usable space, usually measured on the vertical mounting rails. So a piece of equipment that takes up 2U of space, for example, will use 3.5" of rack space. And a 42U rack will offer a total usable space of just over 73”.

One of the most common mistakes that IT professionals make when choosing a rack or cabinet is to make their decision based solely on how many rack units they need to mount all their equipment. The main problem with this thinking is that they often focus only on the primary equipment they want to mount, like the servers, switches, patch panels, and uninterruptible power supplies.  Often little or no thought is given to the secondary equipment they will eventually need to rack-mount such as cable managers and Power Distribution Units (PDUs).  And if you have chosen a rack that barely meets the number of rack units required by your primary equipment, you won't have room to mount the rest of it.

Additionally, when you make a purchasing decision based solely on whether or not a rack has sufficient space to accommodate every piece of your rack-mount equipment, have you left any unused space to allow for airflow and cooling of your high-heat assets like servers? This is critically important when you are evaluating an enclosure that has side panels and or doors because they can act like an Easy-Bake Oven.  Even if your servers are smart enough to shut themselves down when they get too hot (as opposed to just frying the way they all used to), you will still experience a service outage when your server turns itself off.

Finally, if you choose a rack that has the exact number of rack units needed to mount all your current equipment while leaving sufficient air-flow to prevent hot-spots, then you are being short-sighted.  It is always advisable to choose a rack that will also have enough empty space left to accommodate new equipment that will be added to your network in the future.

Tech Tip #1 - Internal Height

The most important considerations concerning the internal height of the rack or cabinet you plan to purchase are to make sure it has:

1. Enough space (rack units) to accommodate all your existing equipment.

2. Extra, unused space to serve as ventilation around servers.

3. Empty space in which future equipment can be mounted as your network grows.

Check back tomorrow for our second segment of this series which focuses on the External Height of racks and cabinets, and the considerations you must weigh before to choosing one.

If you need help installing a new rack or cabinet in your facility, or mounting all of your equipment in it, then contact Tech Service Today for assistance.  We can deliver a skilled Technician to your facility whenever you need help - anywhere in North America.   

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Need help installing, troubleshooting, testing, documenting, or replacing your network cabling?  Call Tech Service Today for on-site technical services anywhere in North America - often in 4-hours or less.

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