Multipath redundant storage system architecture and method

Description

BACKGROUND OF THE INVENTION

a. Field of the Invention

The present invention pertains generally to data storage systems and more specifically to a system and method of interconnection of storage components in fault tolerant data storage systems.

b. Description of the Background

Data storage systems may comprise one or more disc drives connected to one or more disc controllers that are connected to a host or network interface. Each component of the storage system, such as disc drives, controllers, connectors, and wiring are a potential point of failure in the system. Some systems, such as personal computers, for example, may lose access to data in the event of a failure of a controller, bus, or connector. Access to data may require that a failed component be repaired or replaced or that a disc drive be installed in another system to access data. Failure of a disc drive usually results in loss of stored data. Larger storage systems may employ redundancy methods such as RAID to distribute data across a plurality of drives such that data is not lost in the event of a drive failure. In a RAID system, data from the failed drive may be copied from a mirror drive, or the data may be reconstructed from data and parity information on functioning drives. After the failure of a disc or disc controller, the system may often operate in a reduced performance condition until failed components are replaced or repaired. Failure of a bus may require removal of drives and installation of the drives in another fixture or system in order to access data.

The level of fault tolerance, storage capacity, operating life, and data availability are key contributors to the value of a storage system. Fault tolerance may be expressed in terms of the number of failures (both sequential and simultaneous) of discs, controllers, and buses that may be incurred while still maintaining data integrity and data access. Storage capacity reflects the number of disc drives, capacity of each drive, and data encoding methods used. As the number of drives increases, the number of interconnections and likelihood of failure increases. Storage system operating life is reflected in the longevity of components and level of fault tolerance of the system. Spare disc drives may be employed to store copied or reconstructed data to extend operation of the system after the failure of a disc drive. Data availability may be expressed in terms of data transfer rates, fault tolerance, and system performance following failure of one or more components.

The commercial viability of a storage system reflects the architectural decisions and component selections made by the designer to provide a desired level of fault tolerance, storage capacity, operating life, and data availability. Components with very long MTBF (mean time between failure) ratings may adversely affect system cost.

SUMMARY OF THE INVENTION

Embodiments of the present invention furnishes redundant storage system architectures and isolation methods that provide fault tolerance in data storage systems and that can be employed to eliminate single points of failure.

Embodiments of the present invention therefore can comprise a data storage system comprising: a multiple disc assembly containing a plurality of data storage devices disposed within having at least one connector that provides a plurality of signals and that has at least one independent signal for each data storage device of the plurality of data storage devices; a multiple disc assembly receptacle adapted to receive the assembly having a fixture connector that engages the at least one connector; at least one disc controller; and at least one fabric that is configurable such that the fabric can selectively connect the at least one independent signal for each data storage device of the plurality of data storage devices to the disc controller when in a first configuration and can selectively disconnect the at least one independent signal for each data storage device when the fabric is in another configuration.

Embodiments of the present invention can further comprise a multiple disc assembly comprising: a plurality of data storage devices disposed in the assembly; a connector that communicates signals. from the assembly to a fixture adapted to receive the assembly; and a fabric disposed in the assembly in communication with the connector that is configurable to selectively connect and disconnect at least one data storage device of the plurality of data storage devices to at least one signal of the connector.

Embodiments of the present invention can further comprise a removable data storage assembly comprising: a plurality of data storage devices arranged as pairs disposed in the assembly, the assembly having at least two pairs of data storage devices; and a connector that provides external communication for at least one independent signal for each pair of data storage device of the plurality of data storage devices.

Embodiments of the present invention can further comprise a data storage system comprising: a multiple disc assembly containing a plurality of dual ported data storage devices and having at least one connector that communicates at least two independent signals to a fixture and having a first fabric configurable to connect a first port of each data storage device of the plurality of data storage devices to a first signal of the at least two independent signals and having a second fabric configurable to connect a second port of each data storage device of the plurality of data storage devices to a second signal of the at least two independent signals; a multiple disc assembly receptacle adapted to receive the assembly having a fixture connector that engages the at least one connector; and at least one disc controller that can access at least one data storage device of the plurality of data storage devices through the fixture connector.

Embodiments of the present invention can further comprise a method of configuring a data storage system having a multiple disc assembly containing a plurality of data storage devices installed in a multiple disc assembly receptacle and at least one fabric connected to the assembly, said method comprising: detecting an error in said data storage system; identifying one data storage device of the plurality of data storage devices contained in the assembly as being inoperative; and configuring the at least one fabric to isolate the at least one data storage device.

Embodiments of the present invention can additionally comprise a data storage system comprising: a multiple disc assembly containing a plurality of data storage devices and having a connector that provides at least one separate signal line for each pair of data storage device of the plurality of data storage devices; a fixture connected to a host system having a disc controller and fabric disposed within, the fixture having a multiple disc assembly receptacle adapted to receive the assembly and communicate signals therewith; and computer program operable to detect an error in the storage system and to identify an inoperative data storage device in the assembly and to configure the fabric to isolate the inoperative data storage device.

Embodiments of the present invention can further yet comprise a data storage system comprising: a multiple disc assembly containing a plurality of data storage devices and at least one fabric that can be configured to connect and disconnect each data storage device of the plurality of data storage devices to at least one signal of a connector that communicates signals external to the assembly; a fixture having a disc controller disposed within and having a multiple disc assembly receptacle adapted to receive the assembly and communicate therewith; and computer program code that detects an error in the storage system and identifies an inoperative data storage device in the assembly and that configures the at least one fabric to isolate the inoperative data storage device.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 depicts a single-ported disc storage system architecture.

FIG. 2 depicts a dual-ported disc storage system architecture.

FIG. 3 depicts a loop storage system architecture.

FIG. 4 depicts a storage system architecture employing switched single-ported disc drives.

FIG. 5 depicts a storage system architecture employing switched dual-ported disc drives.

FIG. 6 depicts a loop bypass storage system architecture embodiment.

FIG. 7 depicts a loop bypass storage system with two drives connected to each bypass controller port.

FIG. 8 depicts a loop bypass storage system with two dual ported drives connected to each port

FIG. 9 depicts a loop bypass storage system with two dual ported drives connected to each port of a port bypass controller

FIG. 10 depicts a multi-path redundant storage system.

FIG. 11 depicts another multi-path redundant storage system.

FIG. 12 depicts multi-path redundant storage system power distribution

FIG. 13 depicts steps performed by system configuration computer program code operating in a host and/or disc controller

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

Embodiments of the present invention provide redundant components and data paths, and isolation of points of failure within a storage subsystem such that data access may be maintained following failure of a bus or component. Failures may most frequently occur in connectors and components with moving parts, such as disc drives, for example. In general, electronic components, such as integrated circuits, may exhibit a lower rate of failure than connectors or disc drives.

Embodiments of the present invention are applicable to differing storage architectures including systems that employ arrays of single or multiple discs installed in cabinet fixtures and systems that employ removably installable multiple disc assemblies. A multiple disc assembly is defined as a removably installable unit of a predefined size, shape and connector configuration that can contain differing internal data storage devices, components and configurations. In one embodiment, a multiple disc assembly may comprise a first number of 3½-inch discs while another embodiment may comprise a different number of 2½-inch discs. Various multiple disc assembly embodiments may be installed into a single fixture design. This allows a single fixture (cabinet, shelf, etc.) design to be used to produce systems of varying storage capacity, data rate, and processing power. Multiple disc assembly embodiments may vary in complexity, ranging from units that contain only discs and connectors to units that comprise discs, one or more fabrics, one or more disc controllers, and one or more interface controllers. Multiple disc assembly embodiments may employ interfaces such as fibre channel, for example, that allow devices ranging from simple storage devices, to intelligent disc and interface controllers to be used while employing the same connectors. Computer program code operating in a host or other system reflects the complexity of the multiple disc assembly. Multiple disc assemblies may simplify storage system assembly and upgrade, and may reduce the likelihood of radio frequency emissions. A multiple disc assembly receptacle is defined as a receptacle in a shelf, rack, enclosure, or other fixture into which individual multiple disc assemblies that can vary in internal architecture can be removably installed. Embodiments of the present invention may be employed to create storage systems wherein a multiple disc assembly may be considered a “maintenance-free” storage appliance. Multiple disc assembly embodiments may provide one or more spare drives, multiple buses and spare controller capacity such that it may operate for extended periods without user intervention, even after failure of a bus, controller, and/or one or more disc drives. Embodiments of the preset invention may provide levels of fault tolerance sufficient to provide high performance operation after component failures.

FIG. 1 depicts a single-ported disc storage system architecture. System 100 comprises host 102, disc array controller “A” 104, disc array controller “B” 106, bus “A” 108, bus “B” 110, “A” drive array 112, and “B” drive array 114. Drive arrays are depicted as having five drives each. The discs in “A” drive array 112 and “B” drive array 114 are single-ported in that they provide a single interface to either bus “A” 108 or to bus “B” 110. Disc controller “A” 104 and disc controller “B” 106 are connected to host 102 by one or more buses and are dual ported in that they each provide two disc drive bus interfaces. The interfaces of each disc array controller are configured such that either controller can support communications on both bus “A” 108 and bus “B” 110, providing continued operation if either one of the controllers should fail. Depending on the number of disc drives in each array, and the data transfer rates for the drives in the arrays, the system may operate at a reduced data rate after the failure of one of the controllers. Failure of either bus “A” 108 or bus “B” 110, associated connectors, or corruption of bus signals by a connected component, completely inhibits any access to data stored in an array attached to the bus. As such bus “A” 108, bus “B” 110, and any associated connectors and attached components that may corrupt the bus represent a single point of failure. Recovery of stored data requires that either the bus be repaired, or that disc drives be removed and installed in a fixture with a functioning bus. In terms of data availability, the architecture of FIG. 1 may provide reduced availability in the event of a controller failure, or a disc failure that does not affect the bus, and provides no data availability in the event of a bus failure, or failure of a disc or controller that affects the bus.

FIG. 2 depicts a dual-ported disc storage system architecture. System 200 comprises host 202, disc array controller “A” 204, disc array controller “B” 206, bus “A” 208, bus “B” 210, and “B” drive array 212. The discs in drive array 212 are dual-ported in that they each provide a single interface to both bus “A” 208 and to bus “B” 210. Disc controller “A” 204 and disc controller “B” 206 are connected to host 202 by at least one bus, and in the preferred embodiment, at least two buses. Disc controller “A” 204 and disc controller “B” 206 are dual-ported in that they each provide two disc drive bus interfaces. The interfaces of each disc array controller are configured such that either controller can support communications on both bus “A” 208 and bus “B” 210, providing continued operation if either one of the controllers should fail. The dual-ported nature of array 212 allows drives in the array to communicate with either disc array controller. In the event of a bus or controller failure, the system continues to provide data access. Access may be at a reduced rate depending on the transfer rate and number of drives in the array. Compared to the system of FIG. 1, the architecture depicted in FIG. 2 provides the benefit of continued data availability after the failure of a bus, but at the increased cost of using dual-ported disc drives. The architectures of FIGS. 1 and 2 may be representative of systems using parallel or serial bus interfaces such as SCSI, serial SCSI, serial ATA, or fibre channel, for example.

FIG. 3 depicts a loop storage system architecture. System 300 comprises host 302, disc array controller 304, bus 306, and drive array 308. Disc array controller 304 is connected to host 302 by one or more buses. Bus 306 serially interconnects disc array controller 304 and each of the drives of drive array 308 in a loop. Disc array controller 304 and each drive of drive array 308 have on input port and an output port to connected to form the loop of bus 306. The system of FIG. 3 can continue to operate if a disc failure occurs that does not affect bus operation. The failure of the bus, controller, or a disc failure that interrupts bus operation results in loss of data availability, requiring repair of the bus, controller, or disc drive, or installation of drives in another fixture to access data.

FIG. 4 depicts a storage system architecture employing switched single-ported disc drives. System 400 comprises host 402, disc controller “A” 404, disc controller “B” 406, switch control 408, bus “A” 410, bus “B” 412, disc drives 414-422 and switching devices 424-432. Disc controller “A” 404 and disc controller “B” 406 are connected to host 402 by one or more buses and are dual ported that that they each provide two disc drive buses. Bus “A” 410 and bus “B” 412 are connected to both disc controller “A” 404 and disc controller “B” 406. In an alternative embodiment (not depicted), two single port disc controllers can be used wherein a first disc controller provides communication on bus “A” 410 and a second disc controller provides communications on bus “B” 412. Switching devices 424-432 are controlled by switch control 408 and independently connect drives 414-422 to bus “A” 410 or bus “B” 412. Switching devices 424-432 may be any type of switching devices including but not limited to cross-point switches, port multiplexers and the like. Switch control may comprise one or more buses that connect switching devices 424-432 to host 402 and may comprise an 12C bus, RS232, or any other serial or parallel buses. Alternatively, switching devices may be controlled by disc controller “A” 404, disc controller “B” 406, or both. In another embodiment, switch control may employ bus “A” 410 and/or bus “B” 412. As such, switching devices may be controlled directly by host 402, by host 402 through disc controller “A” 410 or disc controller “B” 412, or may be controlled by disc controller “A” 410 or disc controller “B” 412. The architecture of FIG. 4 may employ a larger number of discs and switching devices than depicted. Switching devices can be individually configured for each drive such that each drive employs either bus “A” 410 or bus “B” 412. This allows communication to be maintained in the event of a bus failure, and allows loads to be balanced between buses. The architecture of FIG. 4 provides continued operation in the event of a bus, disc, or controller failure. Switching devices 424-432 may also allow disc drives to be isolated from both buses. In the event of a disc failure, or a disc failure that corrupts bus operation, an associated switching device may be configured to disconnect the drive from both buses. The switching methods shown in FIG. 4 may be applied to dual ported drives where each port of each drive may be selectively connected to bus “A” 410, bus “B” 412, or may be disconnected from both buses. Alternatively, a third bus may be employed to provide higher transfer rates in the event of a bus failure.

FIG. 5 depicts a storage system architecture employing switched dual-ported disc drives. System 500 comprises host 502, disc controller “A” 504, disc controller “B” 506, disc controller “C” 508, switch control 510, bus “A” 520, bus “B” 522, bus “C” 524 and a plurality of drive/switching units beginning with drive/switching unit 512 and ending with drive/switching unit 526. Embodiments are not limited to a specific number of drive/switching units. Drive/switching unit 512 comprises dual ported drive 514, first switching device 516 connected to a first port of drive 514 and second switching device 518 connected to a second port of drive 514. Switching device 516 allows the first port of drive 514 to be connected to bus “A” 520, bus “B” 522, or bus “C” 524. Similarly, switching device 518 allows the second port of disc drive 514 to be connected to bus “A” 520, bus “B” 522, or bus “C” 524. Switching devices are controlled through switch control 510 which may comprise control logic, a bus interface, such as 12C, for example, or other circuitry that allows host 502 to control the function of each switching device. Alternatively, switch control 510 may be connected to one or more disc controllers or one or more buses. Disc controller “A” 504, disc controller “B” 506, and disc controller “C” 508 are connected to host 502 by one or more buses and are dual ported that that they each provide two disc drive buses. Buses 520-524 are each connected to two ports of different disc controllers of disc controllers 504-508 in a manner such that all buses remain operational in the event of a failure of one disc controller that does not corrupt a bus. In another embodiment of the architecture of FIG. 5, switching devices connected to a first port of each disc drive are controlled by a first switch control and switching devices connected to the second port of each drive are connected to a second switch control. The first and second switch controls can be controlled directly by the host, can be controlled by the host through one or more disc controllers connected to the switch controls, or can be controlled by one or more disc controllers. Switching devices may be employed to connect drive ports to one of the buses or may be employed to isolate the port from all buses. Switching devices may comprise any devices configurable to provide the described function including switches, multiplexers, port controllers, cross-point switches, fabrics, etc.

The architecture of FIG. 5 allows system operation to continue after the failure of one or more disc controllers, disc drives, or buses. Additionally, the architecture of FIG. 5 allows data loads to be distributed among disc controllers and buses to optimize performance. Depending upon the number of disc drives, and the data rates of disc drives, the buses, and disc controllers, the architecture of FIG. 5 may provide near optimum performance following the failure of a disc drive, bus, or disc controller. As such the above architecture may be employed in systems where continued high performance is desired following failure of a bus of disc controller.

FIG. 6 depicts a loop-bypass storage system architecture. System 600 comprises host 602, disc controller 604, switch control 606, drives 608-616, switching devices 618-626 and bus 630. Disc controller 604 is connected to host 602 by one or more buses. Bus 630 serially connects disc controller 604 to each switching device of switching devices 618-626 that each either serially connect an associated drive to bus 630 or bypass the drive. When all switching devices are enabled, all drives are serially connected. Switching devices may be controlled by host 602 through switch controller 606 or by disc controller 604. The architecture depicted in FIG. 6 allows disc connections to be individually bypassed such that in the event of a disc failure, or a disc failure that affects bus operation, the failed drive may be bypassed and the system may continue to operate. Switching devices 618-626 may be any type of devices capable of serially connecting or bypassing discs. Switching devices 618-626 and switch control 606 may be implemented as a single unit. Switching devices 618-626 and switch control 606 may comprise a port bypass controller.

Loop bypass methods may be employed to isolate one or more drives. More than one drive may be connected to each port of a port bypass controller. FIG. 7 depicts a loop bypass storage system with two drives connected to each bypass controller port. System 700 comprises host 702, disc controller 704, disc drives 706-724, port bypass controller 726, and bus 728. Drives are arranged in pairs such that drives 706,708 are connected to a first port of port bypass controller 726, drives 710,712 are connected to a second port, drives 714-716, are connected to another port, drives 718,720 are connected to yet another port, and drives 722,724 are connected to still another port. Bus 728 connects disc controller 704 to port bypass controller 726. In an alternative embodiment, two buses may connect the disc controller and port bypass controller, providing redundancy in the event of a bus failure. Any or the ports of port bypass controller 726 may be configured to allow signals to pass through the two drives connected to the port or to bypass the port, providing isolation in the event of a drive failure, or drive failure that corrupts the bus. While FIG. 7 depicts two drives connected to each port of port bypass controller 726, more than two drives may be connected within the scope of the present invention. While FIG. 7 employs a port bypass controller, any devices and configuration thereof that produce the described function may be employed.

Loop bypass architectures may employ a plurality of drives connected to each port wherein each drive is dual ported. FIG. 8 depicts a loop bypass storage system with two dual ported drives connected to each port. System 800 comprises host 802, disc controller 804, disc controller 806, port bypass controller 808, bus 810, port bypass controller 812, bus 814 and disc drives 816-824. Disc controller 804 and disc controller 806 are each connected to host 802 by one or more buses. Disc controller 804 is connected to port bypass controller 808 through bus 810. Disc controller 806 is connected to port bypass controller 812 through bus b. In an alternative embodiment, more than one bus may connect disc controller 804 to port bypass controller 808, and more than one bus may connect disc controller 806 to port bypass controller 812. In another embodiment, each disc controller may connect to both port bypass controllers. Disc drives 816-814 are dual ported and each drive has a first port connected to port bypass controller 808 and a second port connected to port bypass controller 812. As such, each disc drive may be individually configured to connect to a loop formed by bus 810 on one port, or bus 814 on the second port of the drive, or both buses. In the event of a drive failure, or drive failure that corrupts bus signals, the drive may be isolated through configuration of port bypass controller 808 or port bypass controller 812, or configuration of both port bypass controllers. In the event of a disc controller, bus failure, connector failure, or port bypass controller failure, data from drives may be accessed using the functioning disc controller, bus, or port bypass controller.

Two or more dual ported disc drives may be connected to each port of a port bypass controller. FIG. 9 depicts a loop bypass storage system with two dual ported drives connected to each port of a port bypass controller. System 900 comprises host 902, disc controller 904, bus 906, port bypass controller 908, disc drives 910-928, disc controller 930, bus 932, and port bypass controller 934. Disc controller 904 and disc controller 930 are connected to host 902 by one or more buses. Disc controller 904 is connected to port bypass controller 908 through bus 906. Disc controller 930 is connected to port bypass controller 934 through bus 932. Disc drives 910-928 are dual ported and each drive has a first port connected to port bypass controller 908 and a second port connected to port bypass controller 934. In an alternative embodiment, disc controller 904 is also connected to port bypass controller 934 and disc controller 930 is also connected to port bypass controller 908. Port bypass controllers 908 and 934 are individually configurable to provide a connection to a disc drive port or to bypass a connection to a disc drive, allowing each disc drive to be isolated in the event or a drive failure or a failure that corrupts the port connection. Since disc drives are dual ported and two port bypass controllers are employed, the system of FIG. 9 provides continued operation in the event of a disc controller failure, bus failure, or disc drive failure.

FIG. 10 depicts a multi-path redundant storage system. System 1000 comprises host 1002, host bus “A” 1004, host bus “B” 1006, disc controller “A” 1008, disc controller “B” 1010, fabric bus “A” 1012, fabric bus “B” 1014, fabric “A” 1016, fabric “B” 1018, and disc drives 1020-1028. Disc controller “A” 1008 and disc controller “B” 1010 are both connected to host 1002 by host bus “A” 1004 and host bus “B” 1006. Drives 1020-1028 are each dual ported with a first port connected to fabric “A 1016 and a second port connected to fabric “B” 1018. Fabric “A” 1016 and fabric “B” 1018 may include any and all switch types and switching methods including fibre channel fabrics, switches, multiplexers, cross-point switches, port bypass switches, and the like. Fabrics may have address mapped controls and may be controlled by host 1002 through either disc controller “A” 1008 or disc controller “B” 1010. Alternatively, a separate bus, or buses (not depicted), such as I2C, for example, may provide transfer of control and configuration information from host 1002 to fabric “A” 1016 and fabric “B” 1018. Further, fabric “A” 1016 and fabric “B” 1018 may be controlled and configured wholly or in part by disc controller “A” 1008 and/or disc controller “B” 1010. Configuration and control tasks may be shared between host 1002 and disc controller “A” 1008 and/or disc controller “B” 1010.

FIG. 11 depicts another multi-path redundant storage system. System 1000 comprises system interface 1102, system bus “A” 1104, system bus “B” 1106, interface controller “A” 1108, interface controller “B” 1110, interface bus “A” 1112, interface bus “B” 1114, disc controller “A” 1116, disc controller “B” 1118, fabric bus “A” 1120, fabric bus “B” 1122, fabric “A” 1124, fabric “B” 1126, fabric control bus “A” 1128, fabric control bus “B” 1130, and drive groups 1132-1140. Interface controller “A” 1108 and interface controller “B” 1110 connect to a system through system bus “A” 1104 and system bus “B” 1106. The two system buses provide redundant communication paths, allowing continued communication with both interface controllers in the vent that one of the system buses fails. Interface controller “A” 1108 and interface controller “B” 1110 connect to disc controller “A” 1116 and disc controller “B” 1118 through interface bus “A” 1112 and interface bus “B” 1114 that allow continued communication between either interface controller and either disc controller in the event that one of the interface buses fails. Disc controller “A” 1116 and disc controller “B” 1118 are connected to fabric “A” 1124 and fabric “B” 1126 through fabric bus “A” 1120 and fabric bus “B” 1122, providing continued communication between either disc controller and either fabric in the event that one of the fabric buses fails. Fabric control bus “A” 1128 and fabric control bus “B” 1130 provide redundant control paths from interface controller “A” 1108 and interface controller “B” 1110 to fabric “A” 1124 and fabric “B” 1126 and allow configuration of either fabric by either interface controller in the event that either fabric control bus fails. Fabric “A” 1124 is connected to each drive group of drive groups 1132-1140 by separate connection. A drive group comprises one or more drives connected to a fabric by one connection. Drives in the drive groups are dual ported. Fabric “B” 1126 is connected to each drive group of groups 1132-1140 by separate connection. Fabric “A” 1124 connects to one port of the dual ported drive or drives comprising each drive group and fabric “B” 1126 connects to a second port of the dual ported drive or drives comprising each group. The duality of system buses, interface buses, fabric buses, fabric control buses, and drive group connections provides isolation or a redundant path for every data path in the system. The duality of interface controllers, disc controllers, and fabrics, in conjunction with the duality of buses, provides continued operation in the event of a failure of an interface controller, disc controller, or fabric. As such the system depicted in FIG. 11 has no single point of failure relative to buses, controllers, or fabrics.

In addition to buses, connectors, disc drives, fabrics and controllers, isolation and redundancy methods may further applied to power distribution in a storage system such that the system has no single point of failure that might render the system inoperative. FIG. 12 depicts multi-path redundant storage system power distribution. Power is supplied to the system through connector 1202. Alternatively, more than one connector may be employed. More than contact pin within a connector may provide a like voltage, providing a duality of paths in the event that one pin fails to make connection or has higher than desired resistance. Power bus “A” 1204 provides power to local regulator 1208, local regulator 1212, and optionally may provide power to one or more additional local regulators as indicated by local regulator 1216. Local regulator 1208 provides power to fabric “A” 1206. Local regulator 1212 provides power to fabric “B” 1210. Optional regulator 1216 may provide power to disc controller 1214. Other local regulator (not depicted) may provide power to additional disc controllers and to interface controllers, discrete circuitry, or other circuitry such as environmental monitors, for example. Local regulators may be employed to provide power regulated to a desired voltage to components such as integrated circuits that consume relatively low power as compared to disc drives. Systems having redundant interface controllers, disc controllers, and fabrics may employ local regulators for each component, providing continued system operation in the event that a single regulator fails since the redundant component may be employed to access data. Connector 1202 of FIG. 12 also provides one or more pins connected to power bus “B” 1218. Power bus “B” 1218 provides power to voltage regulators 1220 and 1222. Regulators 1220 and 1222 are connected in a manner that allows power to be provided by either regulator and may include isolation circuitry such as diodes or other components. Alternatively, regulators 1220 and 1222 may include input signals that may enable or disable each regulator. Regulators may be controlled by writeable registers, 12C buses, or other signal lines. Voltage regulators 1220 and 1222 provide regulated power to control 1224, control 1228, and optionally to one or more additional controls as indicated by control 1232. Control 1224 controls power to disc group 1226. Control 1228 controls power to disc group 1230. Control 1232 provides power to disc group 1234. Additional control units (not depicted) may control power to additional disc groups, or to other components such as environmental monitors, fans, or other components. Controls 1224, 1228, 1232 and other controls may comprise switches, fuses, breakers, transistors (including field effect transistors, SCRs (silicon controlled rectifiers) or any other devices employed to selectively apply power to a disc group or other components. Controls may include current and/or voltage sensing and may operate in an automatic manner or in response to a control signal. FIG. 12 illustrates that methods of power redundancy and isolation may be applied to data storage system components such that data remains available following the failure of a regulator, and that power to one or more disc drives in a group containing a failed drive may be shut off to conserve power in the system or to isolate components drawing excessive power. As previously noted, data from a failed drive or drive group may be copied or reconstructed and saved using spare capacity of functioning drives. As such, embodiments of the present invention can provide a data storage system that has no single point of failure that would result in data loss.

The foregoing figures have included switches, switching devices, port bypass switches, and fabrics to provide a configurable connection between data storage devices and disc controllers. The term fabric shall refer to any type of device that can provide a configurable connection between data storage devices and disc controllers and shall include fibre channel fabrics, switches, cross-point switches, multiplexers, port bypass controllers and other devices. A fabric may replace the depicted switches, switching devices, or port bypass controllers in the figures.

Embodiments of the present invention can be advantageously employed with a multiple disc assembly (MDA) that comprises a plurality of storage devices and that is inserted into or removed from a cabinet or other fixture as a single unit. The MDA may contain storage devices, may contain storage devices and fabrics, may contain storage devices, fabrics and disc controllers, or may contain data storage devices, fabrics, disc controllers and interface controllers. In other words, embodiments of the present invention as exemplified by the figures may be partitioned between components that are disposed in an MDA and components that are disposed in a cabinet, shelf or other fixture. Such partitioning may reflect MDA size, number of connectors, interface types, drive strength of bus signals, and other factors. In some embodiments, an MDA may employ transversely mounted storage devices where the devices are mounted with the longest axis of the body of at least one storage device orthogonal to the direction of insertion of the MDA into a cabinet, shelf or other fixture. These embodiments allow connectors of storage devices, such as disc drives, for example, to directly engage connectors disposed on a backplane, eliminating intermediate connectors, cables and the like and the additional possible points of failure introduced by intermediate connections.

Computer program code operating in a host system and/or one or more interface controllers, and/or one or more disc controllers is employed to configure fabrics of the present invention. Fabrics may be controlled by computer program code operating in one or more host computers. Such program code may include performance monitoring and load balancing functions. Configuration of fabrics may be performed as a result of a detected failure, or in response to other conditions including load, data type, data size, data storage format, desired response time, etc. as may reflect services provided such as transaction processing, or video streaming, for example. One or more disc controllers may control fabrics. Computer program code operating in a disc controller may configure fabrics in response to a failure or other condition. Configuration of fabrics may be shared between one or more host computers and one or more disc controllers. As previously noted, switch control may employ one or more control buses, such as I2C, may employ one or more disc buses, or both. Fabrics may be mapped as a device on one or more disc array buses and control signals for one or more fabrics may be conveyed across the disc array bus or buses. Some of the figures depict a separate switch control block. In some embodiments the switch control block may be a part of the fabric.

FIG. 13 depicts steps performed by system configuration computer program code operating in a host and/or disc controller. The process of FIG. 13 is applicable to systems like that shown in FIGS. 10 and/or 11. Process 1300 begins at step 1302 where a check is performed to determine if an error condition exists. An error condition may comprise an error such as a read or write error, for example, detected by a disc drive, disc controller, or host system. If the error is detected by a disc drive, the error may be reported to a disc controller and may be checked by a disc controller and/or may be forwarded to a host system. If a disc controller detects an error, the error may be checked and/or may be forwarded to a host system. Alternatively, an error may be detected by a host system. At step 1304, a test may be performed to determine if the host can communicate with interface controller “A” using system bus “A”. At step 1306, a test may be performed to determine if the host can communicate with interface controller “A” using system bus “B”. At step 1308, a test may be performed to determine if the host can communicate with interface controller “B” using system bus “A”. At step 1310, a test may be performed to determine if the host can communicate with interface controller “B” using system bus “B”. Steps 1304-1310 determine if a host or other system is able to communicate with interface controller “A and interface controller “B” using both system bus “A” and system bus “B”. At step 1312, any errors detected in steps 1304-1310 are reported to a host or other system. At step 1314, a check is performed, such as reviewing reported errors, for example, to determine if the host or other system is able to communicate with at least one interface controller. If the host or other system is not able to communicate with at least one interface controller, the process ends at step 1316. If the check performed at step 1314 determines that the host or other system is able to communicate with at least one interface controller, the process continues at step 1318 where a test is performed to determine if disc controller “A” can be accessed using interface bus “A”. This test may comprise reading disc controller registers. At step 1320, a test is performed to determine if disc controller “A” can be accessed using interface bus “B”. At step 1322, a test is performed to determine if disc controller “B” can be accessed using interface bus “A”. At step 1324, a test is performed to determine if disc controller “B” can be accessed using interface bus “B”. At step 1326, any errors detected in steps 1318-1324 are reported. At step 1326, test results are checked to determine if at least one disc controller can be accessed. If no disc controllers can be accessed, the process ends at step 1330. If at least one disc controller can be accessed, the process continues at step 1332 where a test is performed to determine if fabric “A” can be accessed using fabric bus “A”. At step 1334 a test is performed to determine if fabric “A” can be accessed using fabric bus “B”. At step 1336 a test is performed to determine if fabric “B” can be accessed using fabric bus “A”. At step 1338 a test is performed to determine if fabric “B” can be accessed using fabric bus “B”. At step 1340, any errors detected in steps 1332-1338 are reported. At step 1342, test results are check to determine if at least one fabric is accessible. If no fabrics are accessible, the process ends at step 1344. If at least one fabric is accessible, the process continues at step 1346. At step 1346 a test is performed to determine if fabric “A” can access all attached drives. Such tests may comprise reading and/or writing drive registers and/or reading and/or writing data to the drive media. If not all drives are accessible or are not operating properly, fabric “A” may be configured to isolate one or more drives in step 1348 and then the process continues at step 1350. If the test performed in step 1346 determines all drives are accessible and are operating properly, the process continues at step 1350. At step 1350, a test is performed to determine if fabric “B” can access all attached drives. If some drives are not accessible, or are not operating properly, fabric “B” may be configured to isolate one or more drives in step 1352 and the process then continues at step 1354. At step 1354, data from inaccessible or failed drives may be reconstructed or copied and stored on other drives or may be stored on another system such that fault tolerance is provided. I/O commands may be remapped to utilize functioning interface controllers, disc controllers, or fabrics, as identified by pervious tests. The process then ends at step 1356. If the test performed in step 1350 determines that all drives are accessible and operating properly, the process ends at step 1356. The results of tests performed may also be employed to configure power circuitry such as depicted in FIG. 12 such that power is not applied to failed components. The tests performed, the order of tests performed, configuration of fabrics and reconstruction of data and remapping of I/Os may be varied depending on the architecture of the storage system including the number of host buses, interface controllers, disc controllers, number and type of fabrics, and number of disc drives including the number of disc drives attached to each port of the fabric or fabrics. The type of error reported may be used to select a test or set of tests. Alternatively, following a reported error, a range of tests may be run to determine the overall condition of a storage subsystem. A hierarchical order of tests may exist wherein operation of various system components is performed in a predetermined order. The tests performed in FIG. 13 may be executed by a host or other system, or may be executed by components within a storage subsystem. Computer program code performing tests may be resident in individual components of the system or may be transferred from other systems or other components. Tests may include execution of self-test computer program code in components. For example, disc drives may include a power-on self test routine and such routing may be invoked as part of the tests performed in FIG. 13 to check operation of disc drives.

Embodiments of the present invention can be employed to provide maintenance free multiple disc storage assemblies that can be installed and removed in fixtures such as storage cabinets, bays, shelves, and the like. The multiple interface controllers, disc controllers, buses and fabrics allow continued operation following failure of a disc, disc controller, interface controller, connector, or bus. Systems with a large number of drives may employ a third bus as illustrated in FIG. 5 such that system performance can remain high following failure of a bus or disc controller. Various permutations of the disclosed embodiments, including the number of disc drives, disc controllers, interface controllers, buses, type of switching devices and control thereof may be employed within the spirit of the present invention.

The foregoing description has employed various descriptions employing disc drives and disc controllers to illustrate embodiments of the present invention. Embodiments of the present invention are not limited to a specific number of data storage devices and are not limited to the type of data storage device, including storage media type and bus type. Disc controller shall refer to any type of controller employed to access data from storage devices. Disc controllers may also provide fault tolerant data formatting functions such as RAID, ECC, or other formats. Data storage devices may comprise any type of data storage device including electrical, magnetic, optical, or chemical data storage devices including but not limited to hard disc drives, optical drives, RAM drives including solid state memory devices, and the like and may include combinations thereof and further may include combinations of volatile and non-volatile data storage devices. The fabric or fabrics interconnecting one or more disc controllers and one or more storage devices may be any device or devices that allows configurable connections between disc controllers and storage devices and may include interface type and data format translation. For example, a fabric may convert serial attached SCSI storage device data and interface signals into fibre channel signals that are communicated to a controller. Interface controllers may provide interface type and data format conversion and may also execute computer program code to configure one or more fabrics.

The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.