Dynamic Read Scan Interval Adjustment for SSD Data Integrity
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Solution Overview
Problem
Solid-state storage drives (SSDs) face inefficiencies in read scan operations due to high bandwidth and latency requirements, which disrupt host interactions and increase program/erase cycles, necessitating a more intelligent and balanced approach to manage read scan operations, especially in quality-sensitive server applications.
Innovation Solution
A dynamic method is implemented to adjust the read scan interval based on bit error rates and cross temperature metrics, involving a read scanner, error correction code decoder, health manager, and data mover to relocate data and optimize read scan frequency, using temperature sensors and iterative read attempts to determine optimal read levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional periodic read scan operations are implemented, then data integrity is maintained, but host interaction is interrupted and write amplification increases
Solution Approach 1:
The read scan interval is dynamically adjusted based on the health status of storage blocks. The system transitions from fixed periodic scanning to adaptive scanning where the interval changes according to detected bit error rates and block conditions, allowing longer intervals for healthy blocks and shorter intervals for deteriorating blocks
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring bit error rates and block health metrics during read operations. This feedback information is used to adjust future read scan intervals, creating a closed-loop system that optimizes scanning frequency based on actual block conditions rather than following a rigid schedule
2Reliability
If read scan operations are performed frequently, then data integrity is improved, but latency increases and bandwidth is consumed
Solution Approach 1:
The system changes the temporal parameter of read scan operations by adjusting the scan interval duration based on block health. Instead of using a fixed time interval, the system modifies this parameter dynamically, extending intervals for healthy blocks to reduce latency and maintaining shorter intervals only for blocks showing signs of deterioration
Solution Approach 2:
The system applies partial action by performing read scans selectively based on block health status rather than scanning all blocks uniformly. Healthy blocks may skip scans or undergo less frequent scanning, while only problematic blocks receive intensive scanning attention, reducing overall system latency
3Reliability
If read scan operations are implemented, then data integrity is maintained, but program/erase cycles increase leading to write amplification
Solution Approach 1:
The system applies local quality by differentiating treatment for different storage blocks based on their individual health status. Instead of uniform periodic scanning, each block receives scanning attention proportional to its actual need, with healthy blocks experiencing minimal scanning and problematic blocks receiving focused attention, thereby reducing overall PE cycles
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the frequency and impact of read scan operations, minimizing disruptions and extending SSD lifespan by dynamically adjusting scan intervals and relocating data to healthier blocks, thereby enhancing both performance and reliability.
Implementation Method 1
Each memory die includes a temperature sensor. The health manager is configured to determine that the storage block spans a hottest memory die of the plurality of memory die based on a die temperature reported by each temperature sensor.
Implementation Method 2
The error correction code decoder is configured to determine a bit error rate for the data read by the read scanner.
Data Source
AI summary
A method and apparatus for dynamically determining when, or how often, to do a read scan operation on a solid-state storage drive. One solution adjusts a read scan interval as part of performing a read scan operation. First, a bit error rate is determined for one of a plurality of storage blocks of a non-volatile memory array. Then, a cross temperature metric for the storage block is determined. A read scan interval is changed in response to the cross temperature metric satisfying a cross temperature threshold. Then, data in the storage block is relocated to a free storage block in response to the bit error rate satisfying a relocation threshold.