In IT Advisor, cooling redundancy refers to the amount of redundant cooling units in this way:

• N: There are no redundant cooling units for the rack.
  There are one or more coolers in the data center. If ONE cooler fails anywhere in the data center, it would result in inadequate cooling (yellow or red CI).

• N+1: There is one redundant cooling unit for the rack.
  ONE cooler (CRAC, row-based, or OA unit) can fail anywhere in the data center and cooling will still be adequate (green CI).

• N+2: There are two redundant cooling units for the rack.
  TWO coolers (CRACs, row-based, or OA units) can fail anywhere in the data center and cooling will still be adequate (green CI).

• N+x: There are x redundant cooling units for the rack.
  X coolers (CRACs, row-based, or OA units) can fail anywhere in the data center and cooling will still be adequate (green CI).