LTFTL: lightweight time-shift flash translation layer for flash memory based embedded storage

  • Authors:

  • Kyoungmoon Sun;Seungjae Baek;Jongmoo Choi;Donghee Lee;Sam H. Noh;Sang Lyul Min

  • Affiliations:

  • Dankook University, Yongin, South Korea;Dankook University, Yongin, South Korea;Dankook University, Yongin, South Korea;University of Seoul, Seoul, South Korea;Hongik University, Seoul, South Korea;Seoul National University, Seoul, South Korea

  • Venue:
  • EMSOFT '08 Proceedings of the 8th ACM international conference on Embedded software
  • Year:
  • 2008

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Abstract

Flash memory storage has been widely used in various embedded systems such as digital cameras, MP3 players, cellular phones, and DMB devices and now it applies to PCs as a form of SSDs. Characteristics of Flash memory necessitate a software layer called FTL (Flash Translation Layer) that directs modified data to new places in Flash memory and maintains a mapping between a logical sector number to a physical page. We notice that this out-of-place update scheme of the FTL allows a low-overhead time-shifting between multiple versions of storage state. From this observation, we propose LTFTL (Lightweight Time-shift FTL) that provides not only multiple versions of storage state but also an open-ended interface to traverse them. This open-ended interface can be used to support fault-resilience schemes, transactions of various granularities, and user-friendly roll-back services. Experimental results from a prototype implementation show that the proposed LTFTL can (1) provide a low-overhead time-shift capability at the user level by maintaining multiple storage states and (2) enhance the reliability/survivability of Flash memory by allowing to roll back to a previous consistent storage state at the storage system level.