17 Glossary
17
70
Rittal Liquid Cooling Package
17
Glossary
1 U server:
1 U servers are very flat and deep, modern high per-
formance servers, whose height corresponds to one
height unit (1 U = 44.54 mm, the smallest standard
height division). Typical dimensions are (W x D x H)
482.6 mm (19") x 800 mm x 1 U.
These systems normally include 2 CPUs, many GB
RAM and hard drives, so that they require up to
100 m
3
/h cooling air at a maximum of 32 °C.
482.6 mm (19") level:
The front sides of the devices built into the server en-
closure form the 482.6 mm (19") level.
Blade server:
By orienting dual CPU systems vertically and placing
up to 14 units on a common backplane to provide for
signal routing and power supply, one has a blade serv-
er.
Blade servers can "generate" up to 4.5 kW heat loss
per 7 U and 700 mm depth.
"Front to back" cooling principle:
The devices built into the server enclosure are normally
cooled according to the "front to back" cooling princi-
ple.
Under this cooling principle, cold air supplied by exter-
nal air conditioning is blown to the front of the server
enclosure. The fans in the devices built into the server
enclosure direct this air horizontally through the server
enclosure. The air is warmed through this process and
is exhausted out of the rear of the enclosure.
Hotspot:
A hotspot is the concentration of thermal energy in a
small area.
Hotspots normally lead to local overheating and can
cause system malfunctions.
Switch:
Multiple servers normally communicate with one an-
other and in the network using switches.
Because as many inputs as possible are located on
the front of switches, they frequently have an airflow
from the side, not "front to back" cooling.
Hysteresis:
If an upper limit value is overshot (SetPtHigh) or a low-
er limit value is undershot (SetPtLow) a warning or an
alarm will be output
immediately
. For a hysteresis of
x%, the warning or alarm for undershooting an upper
limit value or overshooting a lower limit value clears
only for a difference of x/100*limit value to the limit val-
ue.
