Scanning
How DiskPeek reads your disk, and why it is quick about it.
Results while it works
Most analyzers make you wait for a complete answer before showing you anything. DiskPeek streams what it finds, so the tree is browsable almost immediately and simply fills in as the scan continues.
What makes it fast
Filesystem metadata is read in bulk rather than one call per file, a fixed pool of workers walks directories in parallel instead of spawning a thread for each one, and no filesystem work ever happens on the main thread. That last one is why the window never beachballs.
On a MacBook Pro it walks about six million files in a couple of minutes.
Performance profiles
Settings has a performance profile if you want to tune it. Automatic suits almost everyone. The higher profiles use more CPU and energy, and on some drives they are actually slower because the bottleneck is the disk rather than the app, so try Automatic before reaching for them.
What it will not do
It never reads file contents, never follows a symlink out of the folder you pointed it at, and never crosses onto another volume without being asked. Mount points show up in the results but are not walked into.