Storage Device Read-Only Mode Handling via Virtual Space Manager
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Solution Overview
Problem
Memory devices often enter a read-only mode due to pending die or plane failures caused by bad blocks, which are not mitigated by existing technologies, leading to inability to write data even when other parts have free space, and users are not notified before this state is reached, resulting in data loss and operational limitations.
Innovation Solution
A storage device with a virtual space manager that monitors the health of dies and planes, notifies users of a pending read-only mode, and provides options to cease write operations, backup data, format at half capacity, and perform write operations on remaining good blocks, ensuring continued use and data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the memory device continues to operate in normal write mode, then productivity is maintained, but reliability deteriorates due to pending die/plane failure from bad blocks
Solution Approach 1:
The memory device is segmented into multiple dies and planes, allowing the system to identify and isolate degraded regions (dies/planes with bad blocks) while maintaining operational capacity in healthy regions. The controller can selectively access good blocks within good dies/planes, enabling continued write operations on available healthy memory space even when other regions are degraded.
Solution Approach 2:
The system dynamically changes operational parameters by transitioning from full-capacity interleaved meta block operations to half-capacity operations on remaining good blocks. When degradation is detected, the controller adjusts the write operation parameters to use only available good blocks, maintaining reliability while preserving partial productivity.
2Reliability
If the memory device enters read-only mode to ensure reliability, then data integrity is protected, but ease of operation deteriorates due to inability to perform write operations or formatting
Solution Approach 1:
The system performs preliminary actions by notifying the user of pending read-only mode before it actually enters that state. This advance notification allows the user to backup data or perform formatting operations while the device is still partially operational, preventing complete loss of ease of operation. The notification triggers user action before the critical read-only state is reached.
Solution Approach 2:
The system maintains dynamic operation by allowing write operations to continue on good blocks even when some dies/planes are degraded. Rather than forcing a static read-only mode, the controller dynamically adjusts which blocks are writable based on their health status, preserving ease of operation for available healthy space while protecting data integrity in degraded regions.
3Productivity
If the memory device uses interleaved meta blocks across all planes, then productivity is maximized, but reliability deteriorates when bad blocks prevent meta block formation
Solution Approach 1:
The interleaved meta block structure is segmented into individual block-level units, allowing the system to identify and exclude bad blocks from meta block formation. When a bad block is detected in a particular die or plane, the controller can reconstruct meta blocks using only good blocks from available dies/planes, maintaining reliability while preserving productivity through alternative block combinations.
Solution Approach 2:
The system changes the parameter of meta block composition by transitioning from requiring all planes to be available to using only available good blocks. When degradation occurs, the controller adjusts meta block formation parameters to use half-capacity operations on remaining good blocks, maintaining productivity at a reduced level while ensuring reliability through selective block usage.
Data Source
AI summary
A storage device ensures the use of a memory device with a degraded plane or die prior to the memory device entering a read-only mode. A controller on the storage device may write host data to a meta block formed in an interleaved manner using good blocks in planes on a first memory device. A virtual space manager may monitor dies and/or planes on the first memory device, determine that remaining good blocks on a first die and/or plane are equal to a minimum block threshold, and send a notification of a pending read-only mode on the first memory device. The notification may include an option to cease to perform write operations to the meta block, backup data on the first memory device, format the first memory device at half capacity and form additional meta blocks, and continue perform host write operations on the additional meta blocks.