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Computer Science Colloquia

Friday, October 16, 2015
Vidyabhushan Mohan
Advisors: Mircea Stan and Kevin Skadron
Attending Faculty: Jack Davidson (Chair), Marty Humphrey, Jiwei Lu and Jack Frayer (SanDisk)

1:00 PM, Rice Hall, Rm. 242

Ph.D. Dissertation Defense Presentation
Towards Building Energy Efficient, Reliable and Scalable NAND Flash based Storage Systems


NAND Flash (or Flash) is the most popular solid-state non-volatile memory technology used today. As memory scales and costs reduce, flash has replaced Hard Disk Drives (HDDs) to become the de facto storage technology. However, flash memory scaling has adversely impacted the power efficiency and reliability of flash based storage systems. While smaller flash geometries have driven storage system capacity to approach petabyte limit, performance of such high capacity storage systems is also a major limitation. In this dissertation, we address the power, reliability and performance scalability challenges of NAND flash based storage systems by modeling key metrics, exploring the tradeoffs between these metrics and evaluating the design space to build application optimal NAND flash based storage systems.

To address the power efficiency of flash memory, this dissertation presents FlashPower, a detailed analytical power model for flash memory chips. Using FlashPower, this dissertation provides detailed insights on how various parameters affect flash energy dissipation and proposes several architecture level optimizations to reduce memory power consumption.

To address the reliability challenges facing modern flash memory systems, this dissertation presents FENCE, a transistor-level model to study various failure mechanisms that affect flash memories and analyze the trade-off between flash geometries and operation conditions like temperature and usage frequency. Using FENCE, this dissertation proposes both firmware and architecture level solutions to design reliable and application optimal storage systems.

Finally, to address scalability limitations of flash based high capacity Solid State Disks (SSDs), this dissertation evaluates the bottlenecks faced by conventional SSD architectures to show that the processing power available in conventional SSD architectures severely limit SSD performance at petabyte scale capacity. This dissertation proposes FScale, a scalable distributed processor based SSD architecture that can match the scaling rate of NAND flash memory and enable high performance petabyte scale SSDs.