PWF: Reducing Write Response Time in Flash Memory-based Storage Devices

Abstract

Modern flash memory-based storage devices use write buffer not only to reduce the amount of data actually written to the flash memory but also to quickly respond to each write request. A buffered page is flushed to the flash memory as late as possible, expecting possible future write hits, so long as the buffer manager does not select it as a victim for replacement to acquire free space for newly arrived write request. While this delayed-flushing can maximize the buffer hit ratio, in terms of the write response time, it can be a hurdle for fast write response. SSD can respond to a write request only when selected victim pages are safely written to the flash memory and the requested data are written to the write buffer. In this paper, we propose the Proactive Write buffer Flushing (PWF) scheme that proactively flushes a portion of buffered data to the flash memory during the I/O requests intervals. Our simulation study showed that the proposed scheme effectively reduces the write response time with negligible overhead.