Controlling Your PLACE in the File System with Gray-box Techniques

We present the design and implementation of PLACE, a gray-box library for controlling file layout on top of FFSlike file systems. PLACE exploits its knowledge of FFS layout policies to let users place files and directories into specific and localized portions of disk. Applications can use PLACE to collocate files that exhibit temporal locality of access, thus improving performance. Through a series of microbenchmarks, we analyze the overheads of controlling file layout on top of the file system, showing that the overheads are not prohibitive, and also discuss the limitations of our approach. Finally, we demonstrate the utility of PLACE through two case studies: we demonstrate the potential of file layout rearrangement in a web-server environment, and we build a benchmarking tool that exploits control over file placement to quickly extract low-level details from the disk system. In the traditional gray-box manner, the PLACE library achieves these ends entirely at user level, without changing a single line of operating system source code.