It's Not Where Your Data Is, It's How It Got There

Modern flash devices, which perform updates 'out of place', require different optimization strategies than hard disks. The focus for flash devices is on optimizing data movement, rather than optimizing data placement. An understanding of the processes that cause data movement within a flash drive is crucial for analyzing and managing it. While sequentiality on hard drives is easy to visualize, as is done by various defragmentation tools, data movement on flash is inherently dynamic. With the lack of suitable visualization tools, researchers and developers must rely on aggregated statistics and histograms from which the actual movement is derived. The complexity of this task increases with the complexity of state-of-the-art FTL production and research optimizations. Adding visualization to existing research and analysis tools will greatly improve our understanding of modern, complex flash-based systems. We developed SSD Player, a graphical tool for visualizing the various processes that cause data movement on SSDs. We use SSD Player to demonstrate how visualization can help us shed light on the complex phenomena that cause data movement and expose new opportunities for optimization.