Improving Data Center Efficiency with the Right Server Rack Cabinet

Data center efficiency is a frequent topic among facility managers, but it’s not often that those individuals equate server rack selection and configuration to improving efficiency and performance in their IT infrastructure.

A lot of time is incurred configuring the airflow to maximize efficiency, isolating the cold and hot aisles in order to increase the supply and return air temperatures, and selecting efficient power technologies.

But, the efficiency of the data center can be reduced with poor airflow, or unwanted airflow, through the racks.

Improper rack configuration can even jeopardize equipment in those racks by creating hot spots.

Let’s start with the basics.

Standard Server Rack Dimensions

Rack Height

The most common rack height is 42U (78.7)” but there are other heights available, primarily taller, unless you are looking at a “half rack.”

If you don’t mind using step stool or ladder to access equipment at the top of the rack, you may want to consider a 45U (84”) or 48U (89.4”), which may potentially help reduce floor space in your infrastructure.

If you’re placing equipment in the row such as power distribution units (PDU or RPP) or in-row cooling, they will likely be 78”H.

Rack Width

Rack width is also important. The rail width is 19” but other factors to consider are what type of equipment is going in the rack and how much space is needed on the sides.

Some equipment exhausts air at the sides, so a wider rack is required to accommodate the air flow. Widths typically range from 600mm (24”) to 800mm (32”).

Vertical rack PDU’s are considered 0U because they don’t take up any of the rail space but are commonly mounted on the sides.

However, routing all the power cables to these rack PDU’s in the back of the rack, along with the network cabling, can make it difficult to access equipment and block the exhaust air of the servers.

Trapping this exhaust air in racks creates inefficiency and can potentially cause problems with your equipment. To alleviate this issue, choose a wider server rack.

Rack Depth

Another configuration to consider is the rack’s depth. They commonly range from 825mm (32.5”) to 1,200mm (47.3”) but can scale to 42” and deeper if needed. For example, some network equipment is deeper than others and needs the extra rack depth to run efficiently.

The more room you have, both width and depth, the better the power and network cabling can be maintained and organized without jeopardizing efficiency.

As with rack width, if you don’t have the room at the back of the rack to route cables, you could be trapping heat.

Continuing the conversation about allowing exhaust to escape, let’s talk airflow.

Airflow Management

Most of equipment in server racks have a front to back airflow. To optimize the path of the airflow, it’s best practice to have all the exhaust outlets pointing in the same direction.

It is not uncommon to see the exhaust side of a rack blowing air into an aisle that another rack is pulling air from. If possible, this should be avoided and a hot aisle/cold aisle configuration should be followed.

However, the hot aisle can be an aisle or a chimney.

Server Rack Exhaust Chimney

Chimney racks divert all the hot exhaust air into a common return that is pulled back to the cooling units.

This is a very effective method of making sure hot air is not mixing with cold air, but precautions should still be followed.

First, make sure the equipment at the top of the rack isn’t getting overheated. The rack needs to be deep enough to allow room for the hot air to make its way to the top of the cabinet without adversely affecting the other equipment.

Some server rack exhaust chimneys have a fan assist to pull the air out of the rack rather than letting the air naturally rise.

Secondly, make sure the space at the back of the rack and the chimney itself doesn’t have a positive pressure. This overburdens the fans in the equipment because they are working harder to push the air.

Rear Door Air Flow Enhancer

High-density racks and/or racks with less-than-ideal cabling space may have issues getting the air out of back of the rack simply due to the volume of heat that’s being produced.

If this is a concern in your infrastructure, the rear door can be replaced with one that has built-in fans to pull the air out of the rack and expel it to the hot aisle.

On-the-Door Cooling

Another method of cooling that still uses front to back airflow in a rack but minimizes or eliminates the hot aisle is known as rear door cooling.

This solution takes up very minimal footprint and offers room-neutral cooling. Note that this solution tends to be best suited for higher density rack loads and data centers vs. network closets.

Cable Management and Blanking Tools

Last, but certainly not least, is the matter of cable management and blocking airflow with blanking tools. Allowing enough space for cables using proper management tools is also important.

Implementing a cable management strategy allows the air to freely exit the rack. Tools such as lobster claws, straps, and cable straps can organize your cables while keeping them out of the equipment’s way.

Blanking tools are often overlooked but it is rare to see a rack initially filled.

Most racks start off partially full or even empty and if that empty space is not addressed, a cold aisle/hot aisle configuration is degraded significantly due to the open pathway for hot air and cold air to mix.

Blanking tools such as brush and foam kits can help close the extra space around cable bundles. Or consider a blanking panel which temporarily fills in the gap where a future server may be installed. A side blanking panel close off gaps, or potential hot spots, between the rails and the side of the rack.

Ready to Optimize Your Server Cabinet Space?

The theme here is not to over-complicate your server cabinet space, but to simply stress the importance of rack selection and configuration to minimize the risk of downtime and increase efficiency.

Consider these key questions: What will be installed in the racks? What is the airflow pattern in the data center and through the racks? Is the lack of cable management and blanking tools the weak link in an otherwise consistent hot aisle/cold aisle configuration?

For a highly flexible solution, consider the The Vertiv™ DCE™ Rack System. Designed for easy installation, this rack system allows you to choose from either the preconfigured rack selections or choose from our numerous factory installed accessories and configurations to customize your rack system for your data center needs.

Browse more of our highly reliable server rack cabinets and enclosure solutions.

If you need help making the right rack selection in your IT infrastructure, partner with us. We can help ensure your server rack cabinet promotes scalability and improves efficiency in your data center.

Contact us to learn more.