If you’ve ever been on a tour of The Planet’s data centers, you’ve probably noticed a server segregation of sorts. In one aisle, you see big breadracks of tower servers that resemble desktop computers, and in the next, you find rack-mount servers stacked on top of each other in cabinets. Both form factors can connect to the same Internet with the same speed and performance … and they can even share identical hardware specifications. It may be confusing to see both up and running right next to each other. In fact, as a DC manager, I’m often asked about why we elect to use one over the other. Because the explanation is pretty straightforward, I thought it would be a great topic to cover in my blog debut.

Quite a bit has changed in the way we’ve built data centers over the last four years. When we opened our H2 data center, we only deployed racks of tower servers, and in our newest data center phase, D6 Phase 3, we only provision rack-mount servers. You might assume this shift to imply the complete dominance of rack-mount servers over its tower-chassis relative. Let me suggest that you’d be making an incorrect assumption.

To understand when one form factor may be better than the other, let’s look at the hardware, flexibility, space requirements and costs for each. There are no umbrella claims about rack-mounted and tower servers because each comes in different sizes/variations. Tower servers will generally share the same width, but their heights and depths can vary. Concurrently, rack-mount servers are measured by their heights in “rack units.” The rack-mount server we’ll compare is a 1U – a server that takes up one rack unit of height.

Tower Servers

Hardware/Flexibility: Given the tower server size and layout, it can accommodate a greater number of large components like hard drives, RAID and network cards.
Space Requirements: The benefits of having more space for drives and components come at the cost of taking up more data center space. A breadrack of towers can hold 20 servers, while 30 1U rack-mount servers fill a cabinet less than half the width of the tower racks. There are fewer tower servers in a given square-foot area, so we say that the data center space is less dense. When a data center is dense, it requires more power and more cooling, so a data center with only tower servers will generally require less power and cooling.
Cost: In the early 2000’s, rack-mount servers were nearly twice the price of tower servers, so the use of towers could have been a purely economical decision. Now that the rack-mount equivalent of a tower is available only a few hundred dollars more, a data center’s use of the tower form factor will likely be based on one of the other differentiators.

Rack-Mount Servers

Space Requirements: As we noted, rack-mount servers can be installed more densely in a data center than their tower counterparts. To fit more servers in the same amount of space, the rack-mount servers offer less available interior real estate. Because the server uses less space, it tends to run hotter – the heat emitted from the processor and components is contained in a smaller area – so cooling and air-flow are critically important.
Hardware/Flexibility: A 1U rack-mount server’s decreased real estate often limits the types of components that fit in a given layout and the number of drives that can be installed … it’s not likely that the server above will be employed as a huge network storage repository.
Cost: While the difference in cost between form factors isn’t egregious, the cost of running a data center filled with one or the other is significant. That’s one of the main reasons why you see the focus on efficiency in D6 Phase 3. With more rack-mount servers in a given space, inefficient use of power and cooling means thousands of additional dollars in utility bills.

When it’s all said and done, the form factor of the server you have with The Planet shouldn’t matter to you. You’re connected to the same network, in the same enterprise-class data centers, and you’re getting the same level of service and support regardless of what your server looks like. If you are interested in more the nitty-gritty details from the data center operations side of our business, leave a comment and let me know what you want to see or learn more about, and I’ll do my best to cover it.

-Jon