Response time distribution of flash memory accesses

Flash memory is becoming an increasingly important storage component among nonvolatile storage devices. Its cost is decreasing dramatically and its performance continues to improve, which makes it a serious competitor for disks and a candidate for enterprise-tier storage devices of the future. Consequently, it is important to devise models and tools to analyse its behaviour and to evaluate its effects on a system's performance. We propose a Markov modulated fluid model with priority classes to investigate the response time characteristics of Flash memory accesses. This model can represent well the Flash access operation types, respecting the erase/write/read relative priorities and autocorrelations. We apply the model to estimate response time densities at the chip for an OLTP-type of workload and indicate the magnitude of the penalty suffered by writes under priority scheduling of read operations. The model is validated against a customised hardware simulator that uses input-traces typical of our Markovian workload description. (C) 2009 Elsevier B.V. All rights reserved.