Memory Controller Deletion Request Persistence
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Solution Overview
Problem
Existing memory systems face challenges in effectively managing and persisting logical NAND management information and in-NAND logical-to-physical conversion information, leading to issues with data integrity and recovery during unexpected power shutdowns, particularly when deletion requests are not properly reflected after restart.
Innovation Solution
The memory system includes a memory controller that stores both user data and deletion request data in the NAND memory, along with logical NAND management information and in-NAND logical-to-physical conversion information, ensuring that deletion requests are persisted and can be accurately reflected even after power loss, by associating these with log information and storing them in the NAND memory at predetermined timings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If deletion requests are stored only in volatile memory (RAM), then the system operates quickly with easy access, but data integrity is compromised during unexpected power shutdowns
Solution Approach 1:
The patent applies preliminary action by storing deletion request information in volatile memory (RAM) before power shutdown occurs, and by preparing non-volatile storage (NAND memory) as a backup destination. The system proactively transfers critical deletion metadata to non-volatile storage at predetermined timings, ensuring data integrity is maintained before the harmful event (power loss) can occur.
Solution Approach 2:
The patent uses an intermediary approach by introducing a dual-memory architecture where volatile memory (RAM) serves as the primary fast-storage medium for deletion requests, while non-volatile memory (NAND) acts as a backup intermediary. This intermediary non-volatile storage layer ensures that deletion information persists through power shutdowns, mediating between the speed requirements of volatile memory and the reliability requirements of permanent storage.
2Reliability
If all data including deletion requests are stored in NAND memory, then data persistence is improved, but write operations become slower due to NAND's inherent speed limitations
Solution Approach 1:
The patent applies segmentation by dividing the storage system into two distinct segments: volatile memory (RAM) for high-speed deletion request storage and non-volatile memory (NAND) for persistent storage. This segmentation allows each memory type to operate in its optimal performance zone, with the controller intelligently managing data placement and transfer between segments based on timing and persistence requirements.
Solution Approach 2:
The patent implements local quality by assigning different storage characteristics to different types of data. Deletion request metadata that requires fast access is stored in volatile memory with high write speed, while the same data is selectively transferred to non-volatile memory for persistence. This local optimization ensures that each storage location provides the quality (speed or persistence) most suitable for its specific data type.
3Productivity
If deletion requests are processed immediately without persistence, then system responsiveness is improved, but data loss occurs during unexpected power shutdowns
Solution Approach 1:
The patent applies preliminary action by performing deletion request processing in volatile memory first to maintain system responsiveness, then proactively transferring the deletion metadata to non-volatile memory before power shutdown. This preliminary transfer ensures that even if power is lost, the deletion information is already persisted, preventing data loss while maintaining immediate system responsiveness.
Solution Approach 2:
The patent uses feedback mechanisms where the controller monitors the state of deletion requests in volatile memory and determines when to transfer them to non-volatile storage. This feedback loop ensures that deletion information is persisted at appropriate timings, providing confirmation that data has been safely transferred while allowing the system to continue operating responsively in the meantime.
Data Source
AI summary
A memory system which is accessible to a host device includes a volatile memory, a nonvolatile memory, and a memory controller that controls the volatile memory and the nonvolatile memory. The memory controller stores first data, which is stored in the volatile memory, in the nonvolatile memory, each time the memory controller stores second data, which is stored in the volatile memory, in the nonvolatile memory. The first data indicates a logical address and a deletion range designated by a deletion request received from the host device, and the second data is designated by a write request received from the host device.