Solid State Storage Data Recovery Using Related Page Voltage
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Solution Overview
Problem
Flash memory devices experience data read errors due to charge loss and wear over time, exceeding the capability of error correction codes, leading to uncorrectable errors.
Innovation Solution
A data recovery method for solid-state storage systems that determines optimal reference voltage values by evaluating related pages, using a time-limited search process to adjust voltage thresholds and reduce read errors, allowing for successful data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional error correction codes are used to correct read errors, then some errors can be corrected, but the number of correctable errors is limited and many errors remain uncorrectable
Solution Approach 1:
The patent changes the voltage reference parameter dynamically by determining optimal reference voltage values from related storage elements. This parameter adjustment allows the read operation to accommodate charge loss and wear variations, enabling correction of errors that would otherwise be uncorrectable by fixed-threshold ECC methods.
Solution Approach 2:
The patent performs preliminary action by determining optimal reference voltage values from related storage elements before attempting to read the target storage element. This pre-characterization of voltage thresholds from similar elements (same block, page, or time-programmed elements) prepares the read operation to handle expected charge loss and wear conditions.
2Productivity
If fixed voltage reference values are used for reading storage elements, then the read operation is simple and fast, but read errors occur due to charge loss and wear over time
Solution Approach 1:
The patent applies dynamics by transitioning from fixed voltage reference values to dynamically determined optimal reference voltage values. The reference voltage is no longer static but is adaptively selected based on the characteristics of related storage elements, allowing the system to respond to charge loss and wear while maintaining read performance.
Solution Approach 2:
The patent changes the voltage reference parameter from a fixed value to an optimally determined value based on related storage elements. This parameter adaptation allows the read operation to maintain accuracy despite charge loss and wear, resolving the contradiction between simple fixed-voltage reading and reliable data retrieval.
3Reliability
If optimal reference voltage values are determined by evaluating related pages, then read errors are reduced, but the read process becomes more complex and time-consuming
Solution Approach 1:
The patent uses related storage elements as intermediaries to determine the optimal reference voltage for the target storage element. Instead of directly measuring or calculating the optimal voltage for each element (which would be complex), the system uses voltage values from similar, previously characterized elements as proxies, simplifying the determination process while maintaining accuracy.
Solution Approach 2:
The patent copies voltage reference values from related storage elements (same block, page, or time-programmed elements) to use as optimal reference voltages for the target element. This copying approach avoids complex real-time measurements or calculations, reducing process complexity while achieving accurate voltage thresholds for error reduction.
4Quantity of substance
If multiple voltage reference values are used for MLC devices, then more bits per cell can be stored, but the number of read errors increases due to overlapping voltage distributions
Solution Approach 1:
The patent applies parameter changes by adjusting the voltage reference values to optimal levels determined from related storage elements. For MLC devices with multiple voltage thresholds, this optimization separates overlapping voltage distributions more effectively, reducing read errors while maintaining the ability to store multiple bits per cell.
Solution Approach 2:
The patent applies local quality by determining optimal reference voltage values specific to each block, page, or group of related storage elements. Instead of using a single global voltage reference for all MLC cells, the system tailors the voltage thresholds to local conditions (charge loss characteristics, wear patterns), improving read accuracy for each region while maintaining high storage capacity.
Data Source
AI summary
Embodiments of solid-state storage system are provided herein include data recovery mechanism to recover data upon detection of a read error (e.g., an uncorrectable ECC error) in a storage element such as a page. In various embodiments, the system is configured to determine optimal reference voltage value(s) by evaluating the reference voltage value(s) of page(s) that are related to the page where the failure occurred. The related page(a) may include a page that is paired with the initial page where the failure occurred (e.g., the paired pages reside in a common memory cell), or a neighboring page that is physically near the page where the initial page, and/or a paired page of the neighboring page. In another embodiment, the system is configured to perform a time-limited search function to attempt to determine optimal reference voltage values through an iterative process that adjusts voltage values in a progression to determine a set of values that can retrieve the data.