Server Hardware Explained (Part 1)

If you would like to read the other parts in this article series please go to:


A few years ago I wrote an article series for this site called Networking for Beginners. To date this series remains immensely popular and I routinely receive E-mail messages from readers asking me to continue the series. Unfortunately, continuing the Networking for Beginners series isn’t an option for various reasons, but I wanted to do the next best thing and write a series that is designed to introduce beginners to the basics of server hardware.

The Difference Between PCs and Servers

When I first started out as a network administrator one of the concepts that I had trouble grasping was the difference between a server and a PC (from a hardware standpoint). Don’t get me wrong, learning the differences between a PC and a server isn’t rocket science. It’s just that I didn’t have anyone who could explain it to me.

I got my first job as a network administrator almost twenty years ago during my first year of college. At the time I had a really strong working knowledge of PC hardware and of DOS (which was the desktop operating system of choice at the time). However, I had never been exposed to network servers before. My only background in networking at that point involved IBM mainframes.

Prior to interviewing for the position I memorized a book on Novell NetWare and managed to pass myself off as a networking expert. When I started my new position I didn’t have any trouble working with the network operating system, but I was a bit baffled by the server hardware. I could only assume (incorrectly) that the servers that we were using were highly specialized computers that were only capable of running server operating systems.

A couple of years later Microsoft released Windows NT and I decided to attend a training class to see if Windows NT would benefit our organization. The training center where I took the class provided each student with a PC and then proceeded to teach us how to install Windows NT Server onto it.

This really confused me. I just couldn’t understand why the company that I worked for was spending thirty thousand dollars for each server when a PC that cost a thousand dollars would run Windows NT just as well. Since our servers used exactly the same CPU architecture as our desktop PCs, my only conclusion was that our hardware vendor was ripping us off. After all, it seemed that from a hardware prospective there was absolutely no difference between a PC and a server other than the price.

Obviously I was wrong. I won’t bore you with the details of what the differences between our PCs and our servers were because all of that hardware is completely obsolete today. Even so, I wanted to share this story with you as a way of illustrating the point that there are major differences between PC hardware and server hardware. Sometimes those differences just aren’t immediately obvious to beginners.

In many ways server hardware really isn’t all that different from desktop PC hardware. Both use the same basic components such as memory, CPUs, and power supplies. In spite of these similarities however, server hardware can seem completely foreign to those who have previously only dealt with desktop hardware. The individual components tend to be more advanced than the components that are found in desktop computers. Servers may also make use of redundant and / or how swappable components. Occasionally PCs might have redundant or even hot swappable components, but such features are much more common on servers.

Server Form Factor

So now that I have talked a bit about some of the differences between PCs and servers, I want to turn my attention to server form factors. When it comes to computers, the term form factor describes the physical dimensions and standards used by various system components and by the computer as a whole. To give you a more concrete example, many PCs use a form factor called standard ATX. A standard ATX case can physically accommodate any standard ATX system board and power supply, even if they are made by a different vendor.

Another common PC standard is Micro ATX. Many standard ATX computer cases are designed to accept either standard ATX or Micro ATX system boards, but a Micro ATX case would not be able to accommodate a standard ATX system board because Micro ATX cases use a smaller form factor.

Form factors apply to server hardware as well, but servers typically adhere to different form factors than PCs (but not always). There are several different form factors used for network servers, but the three most common form factors are tower servers, rack servers and blade servers.

Tower Servers

Tower servers look a lot like PCs. Each tower server is a standalone machine that is built into an upright case.

Tower servers are used mostly in smaller datacenters. Larger datacenters typically avoid the use of tower servers because of the amount of physical space that they consume and because they tend to be noisy.

Another disadvantage to using tower servers is that the cabling can get messy. Server racks and blade server chassis usually have features that are designed to manage cables, but tower servers have no such features.

Rack Servers

As the name implies, rack servers are servers that are mounted within a rack. The rack is of a uniform width and servers are mounted to the rack using screws. Each rack can accommodate multiple servers and the servers are typically stacked on top of each other.

Because racks are designed to accommodate standard sized components, many hardware vendors offer rack mountable networking components other than servers. For example there are rack mountable network appliances (such as hardware firewalls) and rack mountable switches.

Rack mount components follow a form factor that is referred to as a rack unit. A standard rack mount server is referred to as a 1U server meaning that it is 1 rack unit in size. A 2U server consumes two rack units of space within the rack. Some vendors also offer 4U and ½U servers. The larger form factors are usually used when the server needs to be able to accommodate a large amount of storage.

Blade Servers

Like rack servers, blade servers also adhere to a standard size and mount inside a special “rack”. In the case of a blade server however, the rack is known as a chassis.

Blade servers tend to be vendor proprietary. You can’t for example insert a Dell blade server into an HP chassis.

The reason why blade server design is proprietary is because unlike a rack server, which is fully self-contained, blade servers lack some of the components that they need to function. For example, blade servers do not have power supplies.

The blade server chassis is designed to accept various modular components, including the blade servers themselves. For example, a chassis might contain a power supply unit, a cooling unit, and a blade server. The actual chassis design varies from one vendor to the next, but most blade server chassis are designed to accommodate multiple power supplies, multiple blade servers, and a variety of other components (such as network adapters, storage modules, and cooling modules). With the exception of the cooling components, individual blade servers are mapped to the individual modules or components.


Now that I have introduced you to the form factors used by server hardware, I want to turn my attention to some other server hardware components. In Part 2 I will be discussing server cases and system boards in more detail.

If you would like to read the other parts in this article series please go to:

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