A 2U rackmount computer usually offers two or three open PCI or PCI-e slots which can come in handy depending on what you want the computer to do.

Since few motherboards come equipped with built-in wireless LAN, you can go ahead and add a PCI-e card and save the USB ports for peripherals like external hard drives. Even if there is dual gigabit LAN onboard that may not be enough if you want to hook up a lot of workstationsso another open slot could be used for a four-port server LAN card.

If the 2U rackmount computer is going to be a workstation, the open slots could be used for one or more high-end video cards. Since most onboard video subsystems share memory with the system RAM going to a video card with dedicated RAM can greatly speed up the system and free up RAM for applications.

If your goal is to make the computer portable by installing it in a portable rack cabinet – which also has the advantage of added protection for hard drives since the whole computer can be shock-mounted –

then you probably want to buy the portable rack before buying the 2U rackmount computer.If you buy the computer first it is important to pay attention to the depth of the case.

Even portable racks that are advertised as being 20 inches deep don’t make all that space available to the components that will go inside it. Some of that space may be used by the front and rear doors or covers. If you make sure to get a computer with a case around 14 to 17 inches in depth chances are good that the computer will fit inside your portable rack with no over hang in the back.

Despite the loss of real estate, many short-depth 2U rackmount computers still allow for up to three 3.5-inch hard drives – necessary if you want to do a RAID 5 setup – a full-size CD-ROM or DVDRW, maybe even a bay for a floppy drive or media reader.

But of even more concern are the available expansion slots. Try to shoot for a case that allows for three full-length PCI or PCI-e slots for your expansion cards. Whether your application is motion control, data acquisition, signal digitizing or any other field operation, it’s these add-on cards that will turn your 2U rackmount computer into a powerful and valuable machine or tool.

Another suggestion is to get as much front access as possible to the things you use most. There are front-mount computer cases that put the slot openings in the front instead of the rear. If access to the I/Os on your expansion cards is important consider getting a computer with a front-mount style case. However, if you’ll be burning a lot CDs or installing software regularly, the standard 2Urackmount computer case with front access to the CDRW is advised.

Usually, with a regular 2U rackmount computer you will have front access to two USB ports. You’ll also get front access to on/off and reset switches as well as power on, hard drive activity and LAN activity LEDs which can come in mighty handy if the system hangs or other problem arises.