Storage Controller Cross-Track Write Atomicity
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Solution Overview
Problem
Database write operations that cross a data storage medium track boundary often fail to maintain atomicity, leading to incomplete writes where a portion of a database page may be stored while another portion is lost, due to failures such as server or storage device failures.
Innovation Solution
A method employing a storage controller with a host adapter and non-volatile storage (NVS) that determines if a write request crosses a track boundary, indicating a two-track transfer and writing data to both tracks in an NVS track buffer. If the host computer fails to provide all data, the method discards the written data to ensure atomicity, and transfers both tracks to different NVS segments only if successful.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a write operation crosses a data storage medium track boundary, then the data transfer capacity is improved, but the atomicity of the write operation cannot be guaranteed
Solution Approach 1:
The patent applies preliminary action by writing data to an NVS track buffer before the actual storage operation. When a write request crosses a track boundary, the system prepares both tracks in advance in the NVS buffer, ensuring that atomicity can be maintained even though the operation spans multiple tracks. This preliminary preparation allows the system to handle cross-track writes atomically by having all necessary data ready before committing to storage.
Solution Approach 2:
The NVS track buffer serves as an intermediary between the host adapter and the final storage medium. This intermediary buffer allows the system to decouple the cross-track write operation from the actual storage commitment, enabling atomicity to be enforced at the buffer level before data is transferred to the storage medium. The buffer acts as a mediator that ensures complete data transfer or complete discard, maintaining atomicity across track boundaries.
2Reliability
If data is written to NVS track buffer for cross-track operations, then write operation atomicity is maintained, but the complexity of the storage controller increases
Solution Approach 1:
The patent applies segmentation by dividing the storage controller into distinct functional components: a host adapter for receiving write requests, an NVS track buffer for temporary data storage, and transfer logic for moving data to the storage medium. This segmentation allows each component to handle specific aspects of the cross-track write operation independently, managing complexity through modular design while maintaining atomicity through coordinated operation of these segments.
3Manufacturing precision
If incomplete data is discarded to ensure atomicity, then data integrity is maintained, but the loss of information occurs
Solution Approach 1:
The patent converts the potential harm of data loss into a benefit by using the NVS track buffer as a safety mechanism. When a cross-track write operation is interrupted, the incomplete data in the buffer is discarded, preventing corrupted data from being written to the storage medium. This deliberate data loss in the buffer prevents greater data integrity violations in the final storage, transforming a negative outcome into a protective measure that ensures overall data consistency.
Data Source
AI summary
A method to maintain write operation atomicity where a write operation crosses a data storage medium track boundary. The method supplies a storage controller comprising a host adapter, a processor, and a NVS. The host adapter receives from a host computer a write request and data. The method determines if the write request will cross a data storage medium track boundary. If the write request will cross a data storage medium track boundary, the method indicates to the host adapter that the write request comprises a two-track transfer, and writes the data to the NVS as the data is received. If the host computer fails prior to providing all the data to the storage controller, the method discards the data written to the NVS to ensure write operation atomicity.