Section: New Results

Flash-based Data Management

Participant : Luc Bouganim.

Bimodal flash devices. While disks have offered a stable behavior for decades, thus guaranteeing the timelessness of many database design decisions, flash devices keep on mutating. Many researchers have proposed to adapt database algorithms to existing flash devices. However, today, there is no reference DBMS design based on solid assumptions of flash devices behavior, precisely because flash device behavior varies across models, across firmware updates and possibly over time for the same model: database researchers are running after flash memory technology. In this study, we took the reverse approach and defined how flash devices should support database management. We advocated that flash devices should provide guarantees to a DBMS so that it can devise stable and efficient IO management mechanisms. Based on the characteristics of flash chips, we defined a bimodal FTL that distinguishes between a minimal mode where sequential writes, sequential reads and random reads are optimal while updates and random writes are forbidden, and a mode where updates and random writes are supported at the cost of sub-optimal IO performance. This work started at the end of 2010 and was published at CIDR'11 [19] , in cooperation with the IT University of Copenhagen. DBMS/Flash device co-design considerations were the focus of a tutorial on flash devices given recently at VLDB 2011 [20] .