Zone Formation for Zoned Namespaces in SSDs
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Solution Overview
Problem
Storage devices, such as SSDs, face issues with the aging and wear of erase blocks, leading to decreased retention ability and increased bit error rates due to frequent program-erase cycles, causing some blocks to become unusable.
Innovation Solution
A method is introduced where a storage device divides its capacity into zones, with a controller comparing the estimated age of available erase blocks across multiple dies to select blocks for each zone, excluding older blocks to form zones and keeping them in a free pool to mitigate wear and optimize usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If erase blocks are frequently used for program-erase cycles to meet storage demands, then productivity is improved, but reliability deteriorates due to increased wear and age
Solution Approach 1:
The patent segments the pool of erase blocks into multiple zones (first zone, second zone, third zone, etc.) based on their age characteristics. Younger erase blocks are placed in later zones while older blocks form earlier zones. This segmentation allows the system to selectively manage wear across different block groups, improving overall reliability while maintaining productivity through balanced usage patterns.
Solution Approach 2:
The patent changes the parameter of block selection by introducing age-based zoning instead of random or round-robin selection. By monitoring and comparing estimated ages of erase blocks across zones, the system dynamically adjusts which blocks are used for new data, ensuring younger blocks are preferentially selected and older blocks are protected from further wear, thus resolving the contradiction between usage and durability.
2Ease of operation
If older erase blocks are continuously used, then ease of operation is improved, but manufacturing precision deteriorates as blocks become damaged and unusable
Solution Approach 1:
The patent implements preliminary action by proactively monitoring the estimated age of erase blocks and organizing them into zones before they become damaged. By predicting which blocks are older and placing them in protected zones, the system prevents future failures rather than reacting to damage after it occurs. This ensures data integrity is maintained while keeping the operation simple for users.
3Reliability
If erase blocks are evenly distributed across zones by age, then reliability is improved, but device complexity increases due to age tracking and zone management
Solution Approach 1:
The patent applies self-service by enabling the storage system to automatically monitor, compare, and reorganize erase blocks into age-based zones without external intervention. The controller autonomously tracks block ages, performs comparisons across zones, and manages the distribution of blocks to appropriate zones, thereby achieving reliable wear distribution while keeping the complexity hidden from users and simplifying operation.
Data Source
AI summary
The present disclosure generally relates to methods of operating storage devices. The storage device comprises a controller and a media unit. The capacity of the media unit is divided into a plurality of zones. The media unit comprises a plurality of dies, and each of the plurality of dies comprising a plurality of erase blocks. The controller is configured to compare an estimated age of a first available erase block in each of the plurality of dies to one another and select one or more of the first available erase blocks from one or more dies of the plurality of dies based on the estimated ages to form a first zone. At least one first available erase block from at least one die of the plurality of die is excluded from the first zone.