SSD Controller Garbage Collection Cycle Stabilization
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Solution Overview
Problem
In solid-state drives (SSDs) with NAND flash memory, the performance cycle of garbage collection fluctuates significantly during random write operations, leading to variations in Input/Output Operations Per Second (IOPS), which affects the memory system's performance stability.
Innovation Solution
A memory system with a controller that calculates and adjusts the gear ratio between host writes and garbage collection writes based on remaining data writable capacity, using an average performance ratio from multiple generations to stabilize the garbage collection cycle and reduce fluctuations in IOPS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gear ratio is adjusted dynamically based on remaining data writable capacity, then garbage collection responsiveness is improved, but write performance stability deteriorates due to repeated fluctuations
Solution Approach 1:
The patent changes the parameter used for gear ratio calculation from dynamic remaining capacity to a fixed threshold value, stabilizing the gear ratio and preventing performance fluctuations while maintaining adequate garbage collection through the threshold-based trigger mechanism
Solution Approach 2:
The patent implements feedback by monitoring remaining data writable capacity and triggering garbage collection when the capacity falls below a predetermined threshold, creating a responsive yet stable control mechanism that prevents performance degradation
2Quantity of substance
If garbage collection is executed frequently to maintain free blocks, then data writable capacity is maintained, but write performance deteriorates due to increased IOPS variations
Solution Approach 1:
The patent applies partial action by executing garbage collection only when the remaining data writable capacity falls below a predetermined threshold, rather than continuously or excessively, thereby maintaining sufficient free blocks while minimizing performance impact
Solution Approach 2:
The patent uses a fixed threshold parameter for triggering garbage collection instead of dynamic adjustment, preventing excessive garbage collection operations and stabilizing write performance while ensuring adequate free block availability
Data Source
AI summary
According to one embodiment, a memory system includes a controller which controls garbage collection for preparing one or more free blocks by writing valid data read from N blocks to one or more blocks of less than the N. The controller calculates a performance ratio between writing of data in response to a request from a host device and writing of data for the garbage collection in accordance with a data writable capacity remaining in a nonvolatile memory, calculates an average performance ratio from calculated performance ratios of M generations including a calculated latest performance ratio, and adjusts a performance cycle of the garbage collection by applying one of the calculated latest performance ratio and the calculated average performance ratio.