Memory Controller Bad Block Redundancy Allocation
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Solution Overview
Problem
Memory systems face performance and reliability issues due to the limited ability to manage bad blocks effectively, leading to reduced lifespan and increased frequency of erase operations, especially in flash-based memory devices where overwriting requires erasing existing data.
Innovation Solution
A memory system that allocates memory blocks into normal and redundancy regions, with the controller managing these blocks by dividing the normal region into user, user overprovisioning, map, and map overprovisioning regions, and the redundancy region into reserved and additional map overprovisioning regions, allowing for efficient replacement of bad blocks and flexible adjustment of map overprovisioning space to maintain performance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If memory blocks are allocated only for normal storage without redundancy region, then storage capacity is maximized, but reliability deteriorates due to inability to replace bad blocks
Solution Approach 1:
The memory device is segmented into a normal region for user data storage and a redundancy region for bad block replacement. This segmentation allows the system to maintain high storage capacity in the normal region while ensuring reliability through the dedicated redundancy region, resolving the contradiction between maximizing storage capacity and maintaining reliability.
Solution Approach 2:
The redundancy region is preliminarily allocated and prepared before bad blocks occur. By pre-allocating memory blocks in the redundancy region for future bad block replacement, the system ensures that reliability can be maintained without compromising storage capacity, as the replacement blocks are already reserved and ready to use.
2Productivity
If erase operations are performed frequently to maintain storage space, then storage availability is improved, but performance deteriorates due to increased erase frequency
Solution Approach 1:
Bad blocks are extracted and isolated into the redundancy region, separating them from the normal storage region. This extraction allows the normal region to maintain high performance by avoiding frequent erase operations, while storage availability is maintained through the automated bad block replacement mechanism that operates in the background without impacting user storage access.
3Reliability
If redundancy region is fully allocated for bad block replacement, then reliability is improved, but map overprovisioning capability deteriorates
Solution Approach 1:
The boundary between the redundancy region and map overprovisioning region is made dynamic rather than fixed. As bad blocks occur and are replaced, the controller dynamically adjusts the allocation, converting map overprovisioning blocks to redundancy blocks only when necessary. This dynamic adjustment allows the system to maintain map overprovisioning capability for performance optimization while ensuring reliability through available redundancy blocks when needed.
Data Source
AI summary
A memory system includes a memory device including a plurality of memory blocks, and a controller in communication with the memory device to control an operation of the memory device, the controller allocating, among the plurality of memory blocks, a normal region and a redundancy region. The controller divides the normal region into a user region for storing user data, a user overprovisioning region for user data management, a map region for storing map data, and a map overprovisioning region for map data management, and divides the redundancy region into a reserved region and an additional map overprovisioning region, and wherein the reserved region, upon determination that a block in the normal region is a bad block, replaces the bad block.