RAID Storage Device Controller Data Restoration
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Solution Overview
Problem
The rebuild process in storage systems with RAID configurations is inefficient due to high load on the storage controller, which deteriorates performance as it needs to read and write data across multiple storage devices, especially when SSDs are used, as the controller becomes a bottleneck.
Innovation Solution
A storage unit with multiple storage devices forming a RAID group, where each device includes a device controller and storage medium, allows for data and parity transfer within the group to restore data locally without relying on the storage controller, reducing the load on the controller during the rebuild process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the storage controller performs data restoration by reading data and parities from multiple storage devices, then data can be restored, but the load on the storage controller becomes large and performance deteriorates
Solution Approach 1:
The patent divides the data restoration function into two parts: the storage controller issues restoration instructions and coordinates the process, while the device controllers of individual storage devices perform the actual data reading, parity calculation, and restoration operations. This segmentation reduces the computational load on the storage controller and distributes the workload to multiple device controllers that can operate in parallel.
Solution Approach 2:
Storage devices are equipped with device controllers that have autonomous capability to perform data restoration operations. When a restoration instruction is received, the device controller independently reads data from storage media, calculates parities, and restores data without requiring continuous intervention from the storage controller, enabling self-service restoration.
2Speed
If the storage controller is a bottleneck during rebuild process, then SSD high-speed access capability cannot be utilized, but the rebuild process can still be completed
Solution Approach 1:
The patent segments the rebuild process into parallel operations executed by multiple device controllers simultaneously. Each device controller independently handles data reading, parity calculation, and restoration for its assigned storage devices, eliminating the storage controller as a sequential bottleneck and enabling full utilization of SSD parallel access capabilities.
Solution Approach 2:
Device controllers prepare and cache necessary data and parity information in advance during normal operations, so that when a rebuild is needed, the restoration process can proceed quickly using pre-prepared data without requiring intensive real-time processing from the storage controller.
Data Source
AI summary
A storage unit includes a plurality of storage devices that form a RAID group, that are coupled to the same bus, and that communicate with each other. Each of the plurality of storage devices includes a device controller and a storage medium. The plurality of storage devices store each of data and parities generated on the basis of the data, the data and the parities being included in RAID stripes. A first device controller of a first storage device included in the RAID group transmits, to the plurality of storage devices included in the RAID group other than the first storage device, an instruction to transfer the data and/or the parities included in the RAID stripes and restores the data or the parity corresponding to the first storage device of the RAID stripes on the basis of the transferred data and the transferred parities.