Reducing Hybrid Disk Write Latency with Flash-Backed I/O Requests

Abstract

One of the biggest bottlenecks in desktop-based computing is the hard disk with I/O write latency being a key contributor. I/O write latency stems from the mechanical nature of hard disks, with seek and rotational delays the major components. Hybrid disk drives place a small amount of flash memory (NVCache) on the drive itself which can be leveraged by the host and has the potential to increase I/O performance and reduce hard disk power consumption. We present an I/O scheduling algorithm, "Flash-Backed I/O Requests", which leverages the on-board flash to reduce write latency. Since flash memory and rotating media have different I/O characteristics, predominantly in random access context, an I/O scheduler can decide which media will most efficiently service I/O requests. Our results show that with Flash-Backed I/O requests, overall write latency can be reduced by up to 70%.