Flash memory is the first credible challenger to disks. It is
semiconductor memory that is nonvolatile like disks, but has
latency 100 to 1000 times faster than disk and is smaller,
more power efficient, and more shock resistant.
In 2008, the price of flash is $4 to $10 per GB or about 2 to 10
times higher than disk and 5 to 10 times lower than DRAM.
Flash memory bits wear out (unlike disks and DRAMs), but wear
leveling can make it unlikely that the write limits of the flash will be
exceeded