High Performance Flash Memory-based Storage System
--Prof. Sang Lyul Min
School of Computer Science and Engineering, Seoul National University


exponentially decreasing the price/capacity ratio

read physical page (chip #, block #, page #) ~ 25us
write physical page (chip #, block #, page #) ~ 300 us
上面兩個都比一般的硬碟快
但是要複寫的話, 要 erase block (chip #, block #) ~ 2ms (慢!)

FTL (Flash Translation Layer) 某 chip 讓 flash 有點假裝成硬碟
Challenges in FTL
* Asymmetry in read and write speeds
* No overwrite is allowed without erasing

聯想到比較遠的 LVM (http://aplawrence.com/Linux/lvm.html)


CPU 的 critical point (198x) 和 flash memory 的 (2007!)



Jim Gray: You might wnat to record everything you
read (10MB/day, 400GB/life)
hear (400MB/day, 16TB/life)
see (1MB/s, 40gb/day, 1.6PB/life)


"Chameleon" system

Virtualization!
(cache)
FRAM (non-volatile) / SRAM as cache


Two Guiding Principles
Make:
(1) The common case fast/power-efficient and
(2) The rare cases simple/resource-efficient


Write buffers optimized for
* small random writes
* large sequential writes

跑 benchmark (PCMark'04)
四到五倍於硬碟的速度!!



volatile Non-volatile
fastest SRAM FRAM?
Cheapest DRAM NAND Flash / HDD

FRAM 好像不是很穩.

Cache Memory 的故事: IBM 360/85 和 IBM 360/91 兩型

IBM PC / Apple / Compaq "PC compatible" !
"Greed ruins all."

Microsoft Winodws NT / UNIX
"Fight among family members ruins all."