Why File systems are hard to debug

I’m building a file system from scratch. Not because I need one—but because debugging what I can’t see is guesswork. Understanding this at the file system level is my first step toward kernel-level observability with eBPF. Most file systems work fine—until they don’t. When something slows down or behaves unexpectedly, you don’t really know why. You just see symptoms: high disk usage, latency spikes, random slowdowns. The problem is simple. The file system is a black box. You can monitor CPU. You can track memory. You can inspect processes. But what actually happens inside the file system—between a read, a write, and the disk—is mostly invisible. That’s where things break. Debugging turns into guessing. You don’t know: which file caused the issue which process triggered it where the latency actually happened And that’s not a tooling problem. It’s a visibility problem. So instead of just studying file systems, I decided to build one. Not for performance. Not for production. But for visib