Memory Controller Backup Page Allocation for Read Error Reduction
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Solution Overview
Problem
In memory systems, particularly in portable electronic devices, there is a challenge in minimizing complexity and performance degradation while maximizing memory device efficiency, especially in handling concentrated read requests which can lead to errors and inefficiencies due to the presence of bad blocks and normal blocks with varying read request frequencies.
Innovation Solution
A memory system and method that detects over-read pages with high read requests, copies data to a backup page in a bad block, and reads from the backup page to reduce errors, and dynamically sets a backup page among normal blocks when errors occur or when no readable pages are available in bad blocks, ensuring stable data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data is read from normal blocks with high read request frequency, then data access speed is maintained, but error rate increases due to concentrated read requests causing read reclaim operations
Solution Approach 1:
The patent creates a backup copy of data from over-read pages (pages with high read request frequency) and stores it in a backup page located in a bad block. When a read request is received for an over-read page, the controller reads the data from the backup page instead of the original page, thereby maintaining data access speed while avoiding errors associated with concentrated read requests on normal blocks.
2Reliability
If backup pages are set in normal blocks, then data redundancy is achieved, but memory device efficiency decreases due to increased complexity and reduced usable space
Solution Approach 1:
The patent converts the harmful effect of bad blocks (which are typically unusable and reduce storage capacity) into a beneficial resource by utilizing them as the location for backup pages. This approach achieves data redundancy and reliability without consuming additional normal block space, thereby maintaining memory device efficiency and avoiding the complexity associated with managing backup pages in normal blocks.
3Reliability
If read requests are distributed across multiple pages, then error rate decreases, but system complexity increases due to additional management operations
Solution Approach 1:
The patent implements a self-service mechanism where the controller automatically detects over-read pages with high read request frequency and autonomously creates backup copies in bad blocks without requiring complex external management operations. The system self-manages the backup page allocation and automatically redirects read requests to backup pages, thereby reducing error rates while minimizing the increase in system complexity.
Data Source
AI summary
A memory system includes: a nonvolatile memory device including a plurality of memory blocks each including a plurality of pages, the plurality of memory blocks including at least one bad block and normal block; and a controller performing a backup operation of copying data from an over-read page into a back-up page when the over-read page whose number of read requests is equal to or greater than a first reference number is detected among the plurality of pages in the normal block, and reading the data from the back-up page in response to a read request for the over-read page after the backup operation, the controller performing an operation of setting a page which is programmable/readable as the back-up page, and not using a page which is unprogrammable/unreadable, among the plurality of pages in the bad block.