Storage Controller Read Reclaim Based on Sample Read Counts
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Solution Overview
Problem
The reliability of data stored in nonvolatile memory devices decreases over time, leading to potential data loss, and existing technologies lack effective methods to address this degradation during read operations.
Innovation Solution
A storage device with a nonvolatile memory device comprising a first and second storage area, where a controller performs sample read operations to estimate read counts and determines optimal locations in the second storage area for writing data from the first storage area, thereby improving data reliability through a read reclaim operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is continuously stored in the same location in nonvolatile memory, then storage capacity is efficiently utilized, but data reliability decreases over time due to degradation
Solution Approach 1:
The controller performs sample read operations before the actual read reclaim operation to estimate read counts and determine optimal destination locations in advance. This preliminary assessment allows the system to proactively migrate data to more reliable areas before degradation becomes critical, thereby improving data reliability without requiring complex real-time monitoring during normal operations.
Solution Approach 2:
The system automatically identifies degraded data and performs self-healing through read reclaim operations. The controller autonomously determines which data needs migration by analyzing read counts and reliability metrics, then automatically relocates the data to healthier storage areas without external intervention, maintaining reliability while managing complexity internally.
2Reliability
If read reclaim operations are performed frequently to maintain data reliability, then data loss is prevented, but performance overhead increases
Solution Approach 1:
Instead of performing read reclaim operations on all data uniformly, the system applies partial action by selectively targeting only those data blocks that show signs of degradation or have high read counts. The sample read operations estimate read counts to identify candidates for migration, ensuring that reclaim operations are performed only when necessary, thus maintaining reliability while minimizing performance overhead.
Solution Approach 2:
The system dynamically adjusts the frequency and scope of read reclaim operations based on measured parameters such as read counts, data age, and error rates. By changing operational parameters adaptively rather than using fixed schedules, the system optimizes the balance between maintaining data reliability and preserving storage operation efficiency.
3Measurement precision
If sample read operations are performed to estimate read counts, then optimal write locations are determined, but operation time increases
Solution Approach 1:
The system performs sample read operations on a selective subset of data blocks rather than all data, using partial action to estimate read counts only where necessary for reliability assessment. This approach achieves sufficient measurement precision for determining optimal write locations while minimizing the time overhead by avoiding exhaustive sampling of the entire storage space.
Data Source
AI summary
A storage device includes a nonvolatile memory device that includes a first storage area and a second storage area. A controller of the storage device controls the nonvolatile memory device and performs a read reclaim operation of reading data stored in the first storage area of the nonvolatile memory device and writing the read data in the second storage area. In the read reclaim operation, the controller is further configured to allow the nonvolatile memory device to perform sample read operations on the first storage area and to determine locations of the second storage area, at which the data are to be written, based on results of the sample read operations.