Patent ID: 6330687
Filing Date: 2001-12-11
Classification: G06F

Abstract:
A fault-tolerant RAID system having N host computers and N storage array controllers with redundancy in the host computers and storage array controllers comprising:N single RAID subsystems, each single RAID subsystem comprising;one host computer,one storage array controller,each host computer electrically connected to a storage array controller by connector means, andone array of direct access storage units comprising a multiplicity of channels, each channel comprising a multiplicity of direct access storage units electrically connected with each other in series by connector means,connector means connecting each storage array controller with one array, each storage array controller with the capacity to control two arrays, andN cores, each core having switching means with an open position and a closed position, and connection means whereby each switching means may be connected to two channel connection means, and whereby each switching means controls the electrical connection between the two channel connection means,each core connected by channel connection means to each channel of the array of a first single RAID subsystem and to each channel of the array of an adjacent second simple RAID subsystem, thereby dividing the N single RAID subsystems into N pairs, each pair comprising a first and a second adjacent single RAID subsystem and one core, and connecting means, the first adjacent single RAID subsystem of one pair being the second adjacent single RAID subsystem of an adjacent pair,the switching means within each core connected to the channels so when the switching means is in the closed position each channel of the array of the first single RAID subsystem of a pair is electrically connected bidirectionally to a single channel of the second single RAID subsystem of the same pair, thereby allowing the storage array controller of the first single RAID subsystem to control both arrays of the pair,indicator connecting means connecting the storage array controller of the first single RAID subsystem of a pair with the core of the pair,the storage array controller of the second single RAID subsystem of the pair providing a normal operating signal to the host computer of the first single RAID subsystem of the pair via connector means when the storage array controller and the host computer of the second single RAID subsystem are operating normally,the storage array controller of the second single RAID subsystem of the pair not providing a normal operating signal to the host computer of the first single RAID sub system of the pair via connector means when the storage array controller or the host computer of the second single RAID subsystem has failed,the host computer of the first single RAID subsystem of the pair providing a closure signal via indicator connector means to the core when no normal operating signal is received from the storage array controller of the second single RAID subsystem of the pair,the switching means being normally open so there is no electrical connection between the channels of one single RAID subsystem and the channels of the other single RAID subsystem of a pair when no closure signal is received by the core,the switching means being changed to the closed position when the core receives a closure signal from the host computer of the first single RAID subsystem of the pair, thereby establishing an electrical connection between the channels of both of the single RAID subsystems of a pair and allowing the functioning controller and host computer of the first single RAID subsystem to control the channels of both the first and second single RAID subsystems of the pair.