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Abstract:
Initially used in digital audio players, digital cameras, mobile
phones, and USB memory sticks, flash memory may become the dominant
form of end-user storage in mobile computing, either completely
replacing the magnetic hard disks or being an additional secondary
storage. We study the design of algorithms and data structures that
can exploit the flash memory devices better. For this, we characterize
the performance of NAND flash based storage devices, including many
solid state disks. We show that these devices have better random read
performance than hard disks, but much worse random write performance.
We also analyze the effect of misalignments, aging and past I/O
patterns etc. on the performance obtained on these devices. We show
that despite the similarities between flash memory and RAM (fast
random reads) and between flash disk and hard disk (both are block
based devices), the algorithms designed in the RAM model or the
external memory model do not realize the full potential of the flash
memory devices. We later give some broad guidelines for designing
algorithms which can exploit the comparative advantages of both a
flash memory device and a hard disk, when used together.
