Problem solve Get help with specific problems with your technologies, process and projects.

## Server form factors: A guide to rackmount, blade servers and more

### GUIDE SECTIONS

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.

This was last published in April 2006

## Content

Find more PRO+ content and other member only offers, here.

### GUIDE SECTIONS

#### Start the conversation

Send me notifications when other members comment.

## SearchWindowsServer

March Patch Tuesday adds several more mitigations for the Spectre and Meltdown exploits, this time for 32-bit server and client ...

• ### CLI vs. GUI: Find the right admin tool for various scenarios

Standard Windows and Linux command-line utilities oftentimes have niche, yet important functionality not available in GUI tools ...

• ### These PowerShell script examples help tidy up code

Even the most grizzled scripting veterans might learn some new PowerShell tips and tricks to tighten their automation code or ...

## SearchServerVirtualization

• ### Considerations for creating a VM for a development environment

Just because admins are working in a test/dev environment doesn't mean they can be lax about creating VMs. There are several ...

KVM virt-manager provides a useful and simple VM management GUI. The console enables VM creation, deletion and troubleshooting. ...

• ### Get cloud computing certified, but don't abandon virtualization

Cloud certification training can help an IT administrator's career, but it's only practical if it aligns with your company and ...

## SearchCloudComputing

• ### Analysts: How to make IBM Cloud services more competitive

To make IBM Cloud more competitive, Big Blue must stand by its enterprise base, while it also satisfies the developer community ...

• ### Don't overlook these practices in software modernization

During app modernization projects, teams commonly overlook basic goals, processes and tools. which can sully app launches as a ...

• ### Google preemptible VMs reduce cloud costs -- with a catch

With its preemtible VMs, Google offers spare compute capacity at a discounted price. But be careful not to run certain apps on ...

Close