File system performance often matters more to the application than disk or storage device performance, because it is the file system that applications interact with and wait for. File systems can use caching, buffering, and asynchronous I/O to avoid subjecting applications to disk-level (or remote storage system) latency.
System performance analysis and monitoring tools have historically focused on disk performance, leaving file system performance as a blind spot. This chapter sheds light on file systems, showing how they work and how to measure their latency and other details. This often makes it possible to rule out file systems and their underlying disk devices as the source of poor performance, allowing investigation ...