A theoretical analysis of lifespan impact on flash memory imposed by erasure code

Each cell of flash memory only survives a nominally given number of write/erasure cycles. Beyond the nominal lifespan, flash memory can still record digital information but the bit error rate increases rapidly with the increment of write/erase cycles. Erasure code is a conventional method used to recover corrupted data, but its redundant data produce a large number of additional writes, making the erasure code seem to be unsuitable for the write-sensitive flash memory. We argue that, erasure code influences the lifespan of flash memory in two conflicting directions: its inherent error correction capability enables the flash memory to survive beyond the nominal lifespan, while its redundant data wear out the lifespan of flash memory by increasing the write/erase cycles. This paper builds a theoretical model to analyze both the two aspects and demonstrates that the erasure code is able to extend the nominal lifespan of flash memory by as many as 30×.