### Essential Guide

Browse Sections
• Blade servers: Big on computing power, small in size
• Small microservers are a large chunk of the market
• Important server lingo

BACKGROUND IMAGE: iSTOCK/GETTY IMAGES

This content is part of the Essential Guide: Server form factors: A guide to rackmount, blade servers and more
Problem solve Get help with specific problems with your technologies, process and projects.

## Expert Robert McFarlane explains what's needed to cool blade servers.

How much air movement does each blade server typically need for cooling?

When all manufacturers follow the ASHRAE Guidelines for listing power and cooling requirements, this will be an easy answer for anyone to obtain. I suggest you check with the manufacturer of your servers before going by "rules of thumb". However, since you asked for "typical requirements", the following may help.

Air quantity (Cubic Feet per Minute, or "CFM") is determined by three things: the Wattage draw of the equipment; the entering air temperature; and the heat rise you are willing to accept as the air goes through the equipment. Without getting into the technicalities of air conditioning, wattage is converted to heat at the rate of 3.4 BTU per watt. (BTU=watts x 3.4). The heat rise is the temperature differential between the air entering and the air leaving the equipment, and is simply called "TD". The formula for air quantity is:

CFM = BTU / TD x 1.08 (The 1.08 correction factor can be ignored for small calculations if you want.)

Common numbers for Blade Servers would be:

Entering Air = 55° F

Exiting Air = 75° F

TD = 20°

Air Quantity = 630 CFM

This is based on a good under-floor air system with the blade center near the bottom of the cabinet, where the cold air comes up from the floor. It also assumes that all spaces above and below it are filled with other equipment or blank panels to prevent warm "bypass air" from getting from the rear of the equipment back to the front and raising the incoming air temperature. If the blade center is mounted toward the top of the cabinet, the entering air temperature will have risen by the time it gets up there, perhaps to 75°F. In this case, either the equipment will tolerate a 95°F discharge temperature (20° TD), or you'll need more air to cool it.

Entering Air = 75° F

Exiting Air = 90° F

TD = 15°

Air Quantity = 840 CFM

Of course, this assumes that the tiny fans in the servers can actually move 840 CFM of air through the equipment. This is one of the reasons some manufacturers are specifying higher operating temperatures, and allowing 25° to 30° TD's. However, even if the specs say higher temps are OK, you can be sure the life of the hardware will be shortened, and that unexplained errors may very well be temperature related. And remember, a standard 25% open perforated tile, under normal "good" conditions (0.1" static pressure), can only pass about 675 CFM of air. Usually you'll get more like 500 CFM. Its not just the capacity of the air conditioners that counts – it's the air that actually gets to your technology.

Hopefully, this will help you determine what you need, whether or not your data center can provide it, and will also keep those expensive servers from burning up or shutting down at inopportune times.

#### Start the conversation

Send me notifications when other members comment.

## SearchWindowsServer

• ### Windows Server certifications retirement plan a blow to admins

This latest decision by Microsoft to drop the MCSA, MCSD and MCSE certifications is another step to push customers toward the ...

• ### Do you need to make Exchange Online backups?

Microsoft has several protective measures in place to let customers restore deleted mail in Office 365, but backup vendors will ...

• ### Updated Exchange Online PowerShell module adds reliability, speed

Microsoft assists Exchange Online administrators who rely on PowerShell by reworking the underlying functionality of several ...

## SearchServerVirtualization

• ### Configure advanced VM settings in vSphere 6.7

Configuring advanced VM settings is no easy task. Some common questions admins ask include where to place VM swap files and how ...

• ### Employ log management best practices to better analyze, protect data

Log files generate vast amounts of data, which negatively affects performance. As a result, admins should build logging ...

• ### VM networking best practices to boost network performance

Admins who familiarize themselves with VM network switches and activity can better understand issues and employ best practices to...

## SearchCloudComputing

• ### Explore the pros and cons of cloud computing

Familiarize yourself with the basics of computing in the cloud, how the market has changed over the years, and the advantages and...

• ### How to protect and manage Azure Pipelines secrets with Key Vault

Follow along with this Azure Key Vault tutorial to securely manage passwords and other sensitive information in an Azure DevOps ...

• ### 7 Google Cloud database options to free up your IT team

Moving data to a cloud database is an effective way to optimize cost and performance for applications. Review seven of Google's ...

Close