Data array having redundancy messaging between array controllers over the host bus

A method for providing inter-controller communications between an active controller and a standby controller configured for redundant communications between a host and a storage device and linked to a host bus, comprising:

• at the active controller, building a message;
• with the active controller, transferring the message to the standby controller;
• with the active controller, writing to a command/reply queue at the standby controller;
• with the standby controller, checking the command/reply queue for a next message;
• and
• upon detecting the next message, processing with the standby controller the transferred message.

A data storage system with redundant data storage, comprising:

• a host processor;
• an active controller controlling access by the host computer device to data storage devices;
• a standby controller controlling access by the host computer device to the data storage devices;
• and
• a host bus communicatively linking the host processor, the active controller, and the standby controller, wherein the active and standby controllers include redundancy messaging mechanisms configured to assert and sample signals on the host bus to provide inter-controller communications over the host bus.

A method for providing inter-controller communications between an active controller and a standby controller configured for redundant communications between a host and a storage device and linked to a host bus, comprising:

• at the standby controller, specifying a range of memory in the standby controller as an interrupt range;
• with the active controller, writing data to the interrupt range of the standby controller;
• and
• at the standby controller, driving a local interrupt.