Flash Storage Memory

Leventhal

flash memory storage computer architecture

article{leventhal:cacm2008,
  title="Flash Storage Memory",
  author="Adam Leventhal",
  journal="Communications of the ACM",
  volume="51",
  number="7",
  month="July",
  year="2008",
  pages="47--51"
}

Flash memory strikes an interesting balance between cost and performance

• Cheaper in manufacturing and power cost than DRAM
• Faster in performance than hard drives and lower power cost

Some basics

• Two main types: NOR, which supports random access, and NAND which is in blocks
• Generally support about a million writes per cell
  • Controller balances writes to prevent hot spots, has large reserves of cells to swap in

Flash is a good alternative to nonvolatile RAM (NVRAM)

• Fast and persistent with better size, cost, and longevity
• Really useful for log-type use, where data must be continually, quickly written to device
  • Small DRAM buffer overcomes write latency issue

Flash is an interesting alternative for new second-level cache

• Same arguments: Flash is mid-way between DRAM and disks in terms of cost, speed, and size

Combining those two uses enables different system designs and new options for hierarchical storage

• Interesting note: Given flash caches, could even slower hard drives be used for very long term storage?
  • They would be cheaper and more power efficient