The cooling fans within each FRU operate as matched pairs with tachometer-controlled spindles and position-synchronized blades for maximum efficiency. Every cooling fan operates from a common power bus so the failure of a power supply will not interrupt the operation of any fans, even those in the same FRU as the failed power supply.
To remove a power/cooling module, turn the thumbscrew collar at the upper right corner to the left until loose then lower the handle down and pull the FRU out of the enclosure. To install one, slide the FRU into the enclosure until it stops, lift the handle fully and turn the thumbscrew to the right until secure. To lock an FRU in place, use a Phillips screwdriver to turn the screw within the thumbscrew collar to the right. To unlock one, turn the screw to the left. Avoid operating a SANnet II 200 SCSI array for more than a few minutes with a power/cooling module removed to maintain optimum cooling.
Enclosure Management Unit Modules
The enclosure management unit (EMU) controls, monitors and reports environmental parameters such as temperature, power supply status and fan speed. The EMU supports industry standard SAF-TE protocols and features three micro-controllers that supervise FRU control, monitoring and reporting functions. These micro-controllers communicate among themselves and with other FRUs using a proprietary protocol across a standard I2C bus.
FIGURE 8: Enclosure Management Unit
One micro-controller is dedicated to communications between controllers and the EMUs using a proprietary protocol across a standard I2C bus. Another micro-controller is dedicated to the reporting of FRU status using the various FRU-mounted light emitting diode (LED) visual indicators. The primary micro-controller supervises the other micro-controllers and performs numerous other functions:
Communications with the serial EEPROM on the disk mid-plane when needed.
Monitoring of power supply status, cooling fan status and temperature sensors.
Control of front-panel system status LEDs and audible alarm reset switch.
Management of a proprietary serial communication link to expansion enclosures.
Each SANnet II 200 array contains two redundant Enclosure Management Unit (EMU), FRUs operating in a master-slave configuration with automated fail-over and fail-back. The master is active and the slave is passive. If the master EMU fails, the slave EMU begins to provide all necessary functions without interruptions until the failed master EMU is replaced. If a slave EMU fails, the master EMU continues to provide all functions without interruptions.
