Storage Device Data Restoration with Parity and Syndrome Codes
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Solution Overview
Problem
Conventional storage devices face challenges in accurately restoring data from nonvolatile memories during abnormal endings due to cell degradation, leading to potential data loss and incorrect data retrieval when there is no read response from nonvolatile memories.
Innovation Solution
A storage device design that includes a data transfer unit for storing data with added parity data and error detection codes in nonvolatile memory, a data reading unit that reads stripes, an additional data adding unit for completing stripes within a predetermined time, a data error checking unit for detecting errors, and a data correcting unit for correcting errors, ensuring accurate data restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is stored in nonvolatile memory during abnormal end, then data can be restored after power failure, but data errors occur due to cell degradation and read failures
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing syndrome data and parity data in the nonvolatile memory along with the user data before an abnormal end occurs. This preliminary preparation enables the error correction function to operate effectively after power restoration, as the necessary correction information is already available without requiring additional read operations from the degraded nonvolatile memory.
Solution Approach 2:
The patent introduces syndrome data as an intermediary element that mediates between the potentially erroneous user data and the correction process. The syndrome data serves as a diagnostic tool to detect errors in read data, while parity data acts as another intermediary that provides the actual correction information. These intermediary data structures enable the system to handle read failures without directly relying on re-reading the problematic user data from the nonvolatile memory.
2Measurement precision
If error correction techniques are implemented, then data accuracy improves, but system complexity increases due to additional processing requirements
Solution Approach 1:
The patent applies segmentation by dividing the error correction process into distinct functional modules: a syndrome data calculation unit that computes syndrome data from user data, a syndrome data storage unit that preserves this data, and an error correction unit that uses both syndrome and parity data for correction. This segmentation allows each module to perform a specific function independently, simplifying the overall system design and making the complex error correction process more manageable and implementable.
3Productivity
If data is restored from nonvolatile memory, then cache memory is replenished, but time is lost due to read operations and potential hung-up states
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing syndrome data and parity data in the nonvolatile memory along with the user data before an abnormal end occurs. This preliminary preparation enables the error correction function to operate effectively after power restoration, as the necessary correction information is already available without requiring additional read operations from the degraded nonvolatile memory.
Data Source
AI summary
A storage device is for restoring the data saved in a nonvolatile memory to a cache memory, even if there is not a read response from the nonvolatile memory. In a data saving operation, parity data of to-be-saved data is generated, and the to-be-saved data and the parity data having CRCs and AIDs added thereto are written into a flash memory. In a data restoring operation, if an operation to read data from the flash memory is not completed within a predetermined period of time, the data reading operation is suspended, and additional data is set. The to-be-saved data having a data error corrected with the parity data is then written into the cache memory.