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An Improved Analytical Expression for Write Amplification in NAND Flash
Agarwal et al. gave an closed-form expression for write amplification in NAND
flash memory by finding the probability of a page being valid over the whole
flash memory. This paper gives an improved analytic expression for write
amplification in NAND flash memory by finding the probability of a page being
invalid over the block selected for garbage collection. The improved expression
uses Lambert W function. Through asymptotic analysis, write amplification is
shown to depend on overprovisioning factor only, consistent with the previous
work. Comparison with numerical simulations shows that the improved expression
achieves a more accurate prediction of write amplification. For example, when
the overprovisioning factor is 0.3, the expression proposed by this paper gives
a write amplification of 2.36 whereas that of the previous work gives 2.17,
when the actual value is 2.35.Comment: 5 pages, 5 figures, accepted by ICNC 201