FindDiskKiller is a native macOS utility for identifying what is keeping a disk busy. It brings app-level disk I/O, CPU, network activity, file activity, and drive-health evidence into a single workspace so you can follow sustained reads and writes from the first visible signal to the app, files, and device behind it.
The product distinguishes between process-level I/O, physical device throughput, and file-layer tracing. That separation matters because cache behavior, APFS copy-on-write, snapshots, and other system activity can make disk numbers look different at each layer; FindDiskKiller shows those differences instead of flattening them into one metric.