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Design and Evaluation of an Efficient Cache Memory Used in Solid-State Disk Drives

Haghdoost, Alireza | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41939 (19)
  4. University: Sharif University of Technology
  5. Department: Computer Engineering
  6. Advisor(s): Asadi, Hossein
  7. Abstract:
  8. In the past two decades, there has been a significant performance enhancement in processors by leveraging nano-scale semiconductor technologies and micro-architectural techniques. At the same time, there has been a limited performance improvement in storage devices. This performance gap results in a performance bottleneck in computer systems. To fill this gap, Solid-State Disks (SSDs) has been proposed in the previous work. Due to not using mechanical parts, SSDs can provide higher performance and lower power consumption compared to hard disk drives. Typically, SSDs use flash memory chips to store user data. Flash memory has some shortcomings such as limited endurance and low write performance. A cache memory can be used to mitigate flash limitations and to improve SSD performance. Using non-volatile memory instead of volatile cache memory can further improve SSD reliability and reduce power consuption. In this thesis, we present a new architecture for SSDs using Phase-Change Memory (PCM). PCM is a non-volatile memory that works based on electrical resistivity levels of materials. As apposed to DRAM memory, PCM can provide higher endurance, much less read/write power consumption, and comparable read/write performance. However, major PCM challenges are less density (almost half of the DRAM counterparts) and limited write endurance. To mitigate PCM limitations, we propose a hybrid cache hierarchy made of PCM and DRAM memories. In the first part of the proposed hybrid cache memory, we use a small DRAM to store highly referenced data. We also use a large PCM memory to increase the total cache hit ratio and to reduce power consumption. The proposed hybrid cache has been implemented using DiskSim simulator and has been experimentally evaluated using standard I/O traces. Our results indicate that the small DRAM memory can serve up to 80% of the total SSD IO request. The results also reveal that the proposed hybrid cache significantly reduces the total power consumption with negligible performance degredation
  9. Keywords:
  10. Flash Memory ; Non-Volatile Memory ; Cache Memory ; Solid State Disk Drive ; Phase Change Memory

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