STAR: Improving Lifetime and Performance of High-Capacity Modern SSDs Using State-Aware Randomizer

2025-11-09

AI Summary

To address retention degradation and consequent SSD lifetime reduction and read-performance deterioration caused by lateral charge spreading (LCS) in 3D NAND flash, this paper proposes State-Aware Randomization (STAR). STAR introduces, for the first time, a cell-state feedback mechanism that dynamically identifies and eliminates weak data patterns susceptible to LCS, thereby significantly enhancing charge-retention robustness. Through multi-level optimization, the randomization module is tightly integrated into the SSD controller’s I/O path with minimal overhead. We implement and evaluate STAR on a simulation platform built from 160 real 3D NAND chips. Experimental results demonstrate that STAR improves SSD lifetime by up to 2.3×, reduces average read latency by 50%, and consistently outperforms conventional randomization schemes under realistic workloads.

Technology Category

• Search and Optimization: Distributed Search
• Reasoning under Uncertainty: Stochastic Optimization
• Constraint Satisfaction and Optimization: Satisfiability Modulo Theories

Application Category

• Search and Retrieval-Augmented AI: Web learning to rank, online learning, and counterfactual learning for ranking
• User Modeling, Personalization and Recommendation: Fairness-aware retrieval and ranking
• Security and Privacy: Data transparency and provenance

Abstract

Although NAND flash memory has achieved continuous capacity improvements via advanced 3D stacking and multi-level cell technologies, these innovations introduce new reliability challenges, par- ticularly lateral charge spreading (LCS), absent in low-capacity 2D flash memory. Since LCS significantly increases retention errors over time, addressing this problem is essential to ensure the lifetime of modern SSDs employing high-capacity 3D flash memory. In this paper, we propose a novel data randomizer, STate-Aware Randomizer (STAR), which proactively eliminates the majority of weak data patterns responsible for retention errors caused by LCS. Unlike existing techniques that target only specific worst-case patterns, STAR effectively removes a broad spectrum of weak patterns, significantly enhancing reliability against LCS. By employing several optimization schemes, STAR can be efficiently integrated into the existing I/O datapath of an SSD controller with negligible timing overhead. To evaluate the proposed STAR scheme, we developed a STAR-aware SSD emulator based on characterization results from 160 real 3D NAND flash chips. Experimental results demonstrate that STAR improves SSD lifetime by up to 2.3x and reduces read latency by an average of 50% on real-world traces compared to conventional SSDs

Problem

• Addressing lateral charge spreading in high-capacity 3D NAND flash memory
• Eliminating weak data patterns causing retention errors in SSDs
• Improving SSD lifetime and read latency through optimized randomization

Innovation

• State-aware randomizer eliminates weak data patterns
• Optimized integration into SSD controller with minimal overhead
• Emulator tests show extended lifetime and reduced latency