The M6625 SAS drive enclosures have dual redundant hot plug SAS I/O modules that allow the controllers to distribute I/Os between the two modules and provides redundant paths should either I/O module become unavailable. The enclosure also has dual redundant hot plug power supplies and dual hot plug blowers. Environmental Monitoring Unit (EMU) functionality is built into the I/O modules in the enclosures and monitors and reports the condition of the power supplies and fans.