Flash Memory Free Block Detection and Dynamic Garbage Collection Switching
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Solution Overview
Problem
The existing SSDs using flash memory can malfunction due to a decrease in the number of free blocks, leading to processing impossibility, as the host apparatus cannot determine when to perform garbage collection based on varying memory control unit specifications, resulting in potential data loss and system failure.
Innovation Solution
An information processing apparatus and method that detects the number of free blocks in nonvolatile memory and switches between a first writing mode (without garbage collection) and a second writing mode (with garbage collection) based on the detected number of free blocks, ensuring timely garbage collection and preventing malfunction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the memory control unit performs garbage collection automatically without host intervention, then the SSD can maintain normal operation, but the host apparatus cannot determine when garbage collection is needed and may not send timely commands, leading to potential malfunction when free blocks are depleted
Solution Approach 1:
The memory control unit monitors the number of free blocks in the flash memory and provides feedback to the host apparatus. When the free block count falls below a threshold, the memory control unit notifies the host, enabling the host to make informed decisions about initiating garbage collection or switching writing modes to prevent SSD malfunction.
Solution Approach 2:
The memory control unit acts as an intermediary between the flash memory and the host apparatus. It manages the complexity of garbage collection internally while providing simplified status information to the host, allowing the host to control garbage collection timing without dealing with the complex details of block management.
2Reliability
If the host apparatus sends frequent garbage collection commands to ensure free blocks are maintained, then the SSD malfunction risk is reduced, but the writing speed and productivity deteriorate due to frequent interruptions
Solution Approach 1:
The writing mode of the SSD is made dynamic and adjustable based on the number of free blocks. The host apparatus can switch between a first writing mode (with garbage collection) and a second writing mode (without garbage collection) depending on the current free block count, optimizing the balance between reliability and productivity in real-time.
Solution Approach 2:
The garbage collection behavior is controlled by changing operational parameters based on free block thresholds. When free blocks are sufficient, garbage collection is disabled to maximize writing speed. When free blocks fall below thresholds, garbage collection is enabled to maintain reliability, thus dynamically adjusting the parameter of garbage collection execution.
3Duration of action of moving object
If the SSD uses flash memory with higher write capacity (such as SLC instead of MLC), then the number of write operations increases, but the cost and device complexity increase
Solution Approach 1:
The host apparatus proactively monitors the number of free blocks and switches to a writing mode that performs garbage collection before the free block count reaches a critical threshold. This preliminary action prevents the SSD from entering a malfunction state, extending the effective lifespan of the flash memory without requiring higher-end storage devices.
Data Source
AI summary
An information processing apparatus which is capable of preventing a malfunction of a storage using flash memory caused by a decrease in the number of free blocks. The information processing apparatus controls a storage that includes a nonvolatile memory and a memory controller that controls the nonvolatile memory. The number of free blocks in the nonvolatile memory is detected, and in accordance with the detected number of free blocks, the memory controller is instructed to switch to one of the following writing modes: a first writing mode in which the memory controller writes data to the nonvolatile memory without performing garbage collection, and a second writing mode in which the memory control unit writes data to the nonvolatile memory and then performs garbage collection.