Disk Array Controller Redundancy for Seamless Device Replacement
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Solution Overview
Problem
Existing disk array systems require operation termination to replace a disk array device due to the lack of redundant configurations, leading to system interruptions when one of the disk array controllers becomes inoperative.
Innovation Solution
Implementing a disk array system with a redundant configuration between disk array controllers of different devices, allowing for continuous operation by maintaining functionality through partner controllers even if one set becomes inoperative.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If a disk array device is replaced, then the faulty device is replaced with a new one, but the system operation must be terminated because both DACs become inoperative
Solution Approach 1:
The patent merges the backup DAC functionality across multiple disk array devices. Specifically, the B-DAC of one device serves as a backup for another device's A-DAC, creating an inter-device redundancy system. This allows replacement of a disk array device without terminating system operation, as the merged backup DAC from another device continues to handle I/O operations during the replacement process.
Solution Approach 2:
The system pre-establishes redundant DAC configurations where each device has both A-DAC and B-DAC, and these are preliminarily configured to work in pairs across devices. When a device needs replacement, the preliminarily established backup DAC from another device is already in place and can immediately take over, enabling seamless replacement without operation termination.
2Ease of repair
If both DACs in a disk array device become inoperative, then the device can be replaced, but system operation must be terminated
Solution Approach 1:
The patent introduces an intermediary backup DAC from another disk array device that mediates between the failed DACs and the system I/O operations. When both DACs in a device become inoperative, this intermediary DAC acts as a temporary controller, receiving and processing I/O commands that would otherwise be handled by the failed DACs, thereby maintaining system reliability during replacement.
Solution Approach 2:
The system provides beforehand cushioning by pre-configuring backup DACs in other devices that can absorb the failure impact. When DACs become inoperative, the beforehand prepared backup DACs cushion the blow by immediately taking over their functions, preventing system operation termination and allowing graceful device replacement.
3Reliability
If a redundant configuration is implemented within each device, then reliability improves, but device replacement still requires operation termination
Solution Approach 1:
The patent extends the redundancy concept from the intra-device dimension to the inter-device dimension. Instead of only having redundant DACs within the same device, the system creates redundancy across different devices by pairing A-DACs and B-DACs from different devices. This dimensional shift enables device replacement without operation termination, as the redundancy now exists in a different spatial and organizational dimension.
Data Source
AI summary
A disk array system comprises plural disk array devices, and each disk array device has two disk array controllers (first DAC and second DAC) for controlling a disk array. In each disk array device, the first DAC has a redundant configuration with a second DAC of any one of the other disk array devices. Likewise, in each disk array device, the second DAC has a redundant configuration with a first DAC of any one of the other disk array devices. Accordingly, because of the failure of a backboard or the like, even if the first DAC and second DAC of a disk array device become inoperative, when their partners in the redundant configurations are operative, the function as the DAC is maintained. Therefore, it is possible to replace a disk array device or the backboard thereof without terminating the operation of the disk array system.