Redundant controller data storage system having an on-line controller removal system and method

A method of on-line removal of a controller from a redundant controller system having a first controller and a second controller, comprising:

• defining the first controller to include a first processor and defining the second controller to include a second processor;
• detecting partial removal of the first controller from the redundant controller system;
• performing a shut-down sequence on the first controller and the second controller, including interrupting the first processor and interrupting the second processor, and completing outstanding memory accesses for the first controller and the second controller;
• defining the first controller to have a first memory, and placing the first memory into a self-refresh mode;
• and
• finishing removal of the first controller from the redundant controller system after coming out of the self-refresh mode by the first memory.

A redundant controller system configured for on-line removal of a redundant controller comprising:

• a first controller including a first memory, a first processor, and a system for early detection of partial removal of the first controller, and wherein upon detection of partial removal of the first controller the first controller performs a shut-down sequence, including completing memory accesses outstanding on the first memory;
• a second controller including a second memory and a second processor, wherein upon detection of partial removal of the first controller the second controller performs a shut-down sequence, including completing memory accesses outstanding on the first memory;
• and
• wherein after completion of the shut-down sequence by the first controller and the second controller the second memory is placed into a self-refresh mode, and removal of the first controller from the redundant controller system is completed.