Individual Rack Unit
The Individual Rack Unit or IRU was introduced with the Altix 4000 family, but continues to appear in subsequent SGI products.
As originally introduced it essentially allows a blade center approach to housing system components, using the NUMAlink interconnect between them. The IRU is 5U for the Altix 450 and 10U for the Altix 4700 and supports 5 or 10 blades, of which 1 or 2 are double-width slots, respectively. For more information about configuring IRUs, see the Altix 450 or Altix 4700 product pages.