Distributor Rutronik is offering low vibration fans from Delta Electronics for 19in. slide-in 1U rack servers.

"By balancing the propellers both on the outer and inner edges, the fan vibrations, which are especially problematic for hard drives, are reduced up to 50%," said Rutronik.

The standard fan is the 40x40x28mm FFB series.

Then for particularly hot processors there is the GFB series, either 40x40x48mm or 40x40x56mm, with two propeller units attached in series one behind one another.

Both units are separated by a stator and run in opposite directions.

"The stator smoothes the swirling air coming out of the first fan and guides it precisely into the second," said Rutronik.

"This approach improves the overall pressure, the air flow, and the degree of efficiency significantly compared with normal fans that are mounted behind one another."

At lower rack temperatures, the speed of both propellers can be reduced without letting the air flow fall below a critical level to reduce vibration as well as background noise.

It is also possible to optionally disable one of the propellers - and if the first propeller stops, the second automatically takes over.

For more info, see www.rutronik.com