Fault tolerant storage controller utilizing tightly coupled dual controller modules

摘要

A fault tolerant storage controller utilizing tightly coupled dual controller modules. The controller modules each check to see if another controller module or cache module is present and, if so, then all configuration information with respect to the controller modules and attached devices are shared between them. Configuration information may be entered into either or both of the controller modules and the information is shared dynamically. Each cache module may be "locked" by an individual controller module to prevent the other controller module from inadvertently disturbing the contents of the other controller module's cache. During initialization, each controller module checks for the existence of an associated cache module and, if present, it is immediately "locked" by the controller module. Should a controller module fail or give an indication of a malfunction, the other controller module will disable or "kill" the malfunctioning controller module thereby resetting it and releasing any lock it may have had on its cache module. In those instances where the cache module is a write cache, the surviving controller module can resume operations where the malfunctioning controller module left off and complete any remaining writes to the disabled controller module's storage devices preventing the loss of any host computer data. The controller modules are tolerant of the other controller module failing and then rebooting and the sequence of events is detected and recognized by the surviving controller module such that it does not disable the one that failed. The dual controller modules communicate asynchronously to verify that they are each operational and to exchange and verify configuration information and to provide operational status dynamically.