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ESP: Improving Performance and Lifetime of High-Capacity 3D Flash Storage Using an Erase-Free Subpage Programming Technique
http://doi.org/10.5626/JOK.2023.50.1.1
Recent high-capacity 3D NAND flash devices have large page sizes. Although large pages are useful in increasing flash capacity, they can degrade both the performance and lifetime of flash storage systems when small writes are dominant. We propose a new NAND programming scheme, called erase-free sub-page programming (ESP), which allows the same page to be programmed multiple times for small writes without the intervention of the erase operation. By avoiding internal fragmentation, the ESP scheme reduces the overhead of garbage collection for large-page NAND storage. Based on the proposed ESP scheme with an adaptive retention management technique, we implemented an ESP-aware FTL(subFTL) and performed comprehensive evaluations using various benchmarks and workloads. The experimental results showed that an ESP-aware FTL could improve the IOPS and lifetime by up to 74% and 177%, respectively.
New Flash Commands for Building Flash Storage Systems with Plausible Deniability
Geonhee Cho, Myungsuk Kim, Jihong Kim
http://doi.org/10.5626/JOK.2022.49.2.120
Traditional encryption cannot defend against coercive attackers who compel the user to hand over decryption keys as it cannot hide the existence of the ciphertext. To solve this problem, there have been studies on a deniable storage solution that applies plausible deniability, a characteristic that allows the user to deny the existence of sensitive data, to a storage device. The hidden volume mechanism is being used in various deniable storage solutions due to its relatively low-performance overhead compared to other mechanisms, and has recently evolved to defend against multiple-snapshot attacks. However, the existing hidden volume mechanism fundamentally requires a dummy random data pool to hide the ciphertext. Due to the existence of dummy random data stored in the storage device, the plausible deniability characteristic is exposed, which can reveal the intention to hide the data. This study proposes a flash chip-level access control command set that simultaneously supports data sanitization and plausible deniability, and using this, we propose a hidden volume-based deniable storage solution that supports plausible deniability characteristics without dummy random data.
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