Server Hardware Explained (Part 2)

by [Published on 15 Sept. 2011 / Last Updated on 15 Sept. 2011]

This article continues the discussion of server case design by describing some of the features of server cases.

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

Introduction

In my first article in this series, I talked about the various form factors used by network servers. Although it might at first seem a bit odd, I want to turn my attention to server cases. My reason for doing so is that server cases often have a number of features that are designed to support the server’s overall wellbeing. Since my goal in writing this series is to educate novices on server hardware I wanted to start at the beginning.

Cooling Features

Computers must be kept cool in order to function properly. All kinds of bizarre errors can occur if a system's processor begins to overheat. Servers use devices such as heat sinks and CPU fans to keep components cool, but the case design also plays a vital role in regulating the server's overall temperature. Blade servers however, are the exception. The blade server chassis is responsible for cooling the individual blade servers. For rack mount and tower servers however, the case is specifically designed to keep the server cool.

The actual cooling features that are found in a server's case vary from one server to the next. At a minimum, a server typically has at least a couple of case fans. The fans are arranged in a way so that cool air is pulled into the server through vents. This cool air passes over the individual system components and is then exhausted from the system's case. The size of the fans and the number of fans used can vary considerably depending on the case design.

Some server cases rely solely on case fans that really aren’t much different from those found in PCs. Others use a more creative design. For example, I recently saw one server that was equipped with exhaust fans located between each expansion slot.

Servers are also typically equipped with temperature sensors. Sometimes these sensors are integrated into the system board or into individual components, but they may also be built into the case. If the temperature inside the case begins to rise then the fans will spin faster in an effort to keep the server operating at a safe temperature. The system BIOS usually also has a safety mechanism that can shut down the server before damage occurs if the temperature gets to be too high.

Filtering

Sometimes fans alone are not enough to keep a server cool. In industrial areas a server’s fans can suck in dust, dirt, soot, and other contaminants. These particles can clog air vents and may also prevent fans from operating efficiently. In order to prevent this type of contamination, some (but certainly not all) server cases are equipped with built in air filters.

Air filters do a good job of keeping stray particles of contaminants out of a server case, but they require routine maintenance. Air filters (which are usually washable) must be cleaned on a regular basis. A dirty air filter can actually restrict air flow just as badly as if the server’s vents were completely obstructed.

Physical Security

Physical security doesn’t seem to be a major priority when it comes to server case design. Many server manufacturers seem to assume that servers will be placed in physically secure datacenters, so there is little need for physically secure server cases. However, there are aftermarket server cases that are designed to provide good physically security. Such cases are usually key lockable and are often made of heavy gauge steel.

Status Indicators

Servers almost always have various forms of status indicators. The status indicators are typically LED lights. Status LEDs are not unique to servers. PCs also use status LEDs. For example, almost every PC has a power indicator and a hard drive activity indicator. Servers offer such indicators too, but often include additional indicators that are not usually found on PCs.

Each server manufacturer uses their own proprietary set of indicator lights. However, there is usually a global indicator light that can convey the server’s status through colors and / or flash patterns.

Some servers also have a locate light. The idea behind the locate light is that when you are managing a server in a large datacenter it can sometimes be difficult to figure out which physical machine you are connecting to. The locate light helps you to spot the machine that you are managing. For example, if you were to connect to a server using a management tool and then discovered that the server needed to have a hardware component replaced. You could illuminate the server’s locate light and use it to figure out which physical server needs to be repaired. Not all servers have locate lights, and on some servers the simple act of connecting to the server with a management tool causes the locate light to illuminate.

In addition to the status indicator LEDs, there are a few server cases that have integrated thermometers that visually display the temperature inside the case.

Ports

In most datacenters, servers are only accessed remotely. Even so, servers typically include keyboard, video, and mouse ports. These ports can be used during the initial setup or in those rare situations in which it is necessary to perform diagnostics locally.

In the case of blade servers, individual blade servers do not include keyboard, video, and mouse ports. These ports are provided through the blade server chassis.

In addition to the keyboard, video, and mouse ports, servers also typically include USB ports. It is becoming more common for servers to provide USB ports in place of keyboard and mouse ports since USB ports take up less space and can be used as a keyboard or mouse connection.

Drive Bays

Most servers contain at least one or two drive bays. The biggest determining factor in the number of drive bays that a server can accommodate is its form factor. For example, a 1U server might only have one or two drive bays, while some 4U servers offer dozens of drive bays.

Servers with smaller form factors often use local hard drives solely for the operating system and connect to remote storage (such as a SAN) for everything else.

Swing Out Bezels

Another set of features that are often found on rack mount servers are swing out bezels. To help you to understand what swing out bezels are and why they are important, imagine for a moment that you have a rack with half a dozen or so servers installed in it. Now, imagine that you need to add some memory to one of the servers that is located in the middle of the vertical stack. How do you do it? The top, bottom, and sides of the server are all blocked. You could remove the server from the rack, but that’s a lot of work for a simple memory upgrade.

This is where swing out bezels come into play. Swing out bezels allow you to slide the entire server forward so that you can open the server’s case without having to remove the server from the rack. The There are various designs for swing out bezels, but they are usually integrated into a server’s side rails.

Conclusion

Now that I have talked about server case hardware, I want to turn my attention to server system boards, especially with regard to the management capabilities that are built into them.

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

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