Throttling accesses to flash based memory in a combined storage device

摘要

A storage system contains a controller 102, a flash memory 106 and another type of storage device, such as a hard disc drive 108. The flash memory has a life span based on the number of write/erase cycles for each block. The controller estimates the remaining lifespan of the flash memory. Based on the estimate, it determines which data should be written to the flash memory. A limit may be placed on the size of data transfer written to the flash memory. Data transfers over the limit are written to the other storage device without being written to the flash. A limit may be placed on the amount of data pre-fetched from the other storage device during read operations. A proportion of transfers to the system may be written directly to the other storage device and not to the flash memory.