What does the term units mean in the context of server racks, for instance 4U? It is an indication of height, so does that mean the amount of disks the rack can hold or can the rack hold multiple motherboards / processors?
4U indicates that the server needs 4 units of space from the rack which has (for example) 42U of space over all.
Recently I had to deal with lab refinement work and I'm still on that page, here's some more info from Wikipedia.
A rack unit is 1 3/4 inches. There are 3 holes in the rack for screwing equipment in. There is a 1 inch gap between two of them and 3/4 inch gap to the next. Rack mountable equipment will have mounting screws or rails with mounting screws spaced properly to take advantage of this standardized spacing.
If you're starting to look at RU (Rack Units) and other metrics to consider when filling a cabinet, three other items to consider would be: the total power used by the system (Watts), the power used by the system at startup (Watts - generally higher than the 1st metric) and the amount of heat the system is going to generate (BTU). I've seen poorly planned environments where breakers will throw or systems shutdown because of temperature.
Cheers,
Keith
Actually I was wondering if a rack (a single one that is) could be holding more than one motherboard, but it seems it does not. Thank you for your responses.
a rack holds server... a blade system can hold multiple boards (blades). a rack can can hold multiple blade systems... but a motherboard needs a case. if this case is rackmountable... and so on...
Ok, thanks. So it is "blade" what I was looking for.
a blade is a system and not something you can assemble with your own hardware... the blade chassis/rack/plattform is a case that can hold multiple blades.
i'll give you some example from oracle/sun:
Sun Blade Servers