Abstract: Described is a technique for asynchronous event notification in a data storage system. Lower level software, such as a device driver or other software application generating events, reports the occurrence of an event to an event handler. The event handler implements an event reporting policy which may include event consolidation. The event handler reports the events to an event dispatcher which notifies event subscribers of the occurrence of events in accordance with registration information of each subscriber. The event handler may execute in kernel mode or user mode depending on the particular execution mode of lower level software initially reporting the occurrence of events. There may be a hierarchical arrangement of multiple event dispatchers in connection with event reporting. Event dispatchers may implement data sharing of registration information.