The SR645 server has up to eight 40 mm dual-rotor hot-swap fans. Six fans are needed when one processor is installed and eight fans are required when two processors are installed. The server offers N+2 redundancy. The server also has one additional fan integrated in each of the two power supplies.

Depending on the configuration, the server will need either Standard fans (21K RPM) or Performance fans (24K RPM)

Under the following conditions, Standard fans can be used:

   Processor with 120W TDP, and the following requirements:
       No GPUs
       No InfiniBand CX-6 adapters
       No rear drives (2.5-inch or 7mm)
   Processor TDP ? 170W, and the following requirements:
       No GPUs
       No InfiniBand CX-6 adapters
       No rear drives (2.5-inch or 7mm)
       4x 2.5-inch front drive backplane or 8x 2.5-inch front drive backplane

If any conditions are not met, Performance fans are required.