How does APFS actually track which blocks are free across storage tiers? Our new post cracks open the Space Manager's on-disk structures: chunk tracking, free queues, internal pool, and allocation zones.

https://jtsylve.blog/post/2026/06/02/APFS-Space-Manager
#dfir #apfs

Space Manager

In our earlier post on Containers, we introduced the Space Manager as the subsystem responsible for tracking which blocks are in use across all storage tiers and for allocating and freeing blocks on behalf of volumes. That post promised more detail in the future. Today we deliver on that promise by examining the Space Manager’s on-disk structures, including its hierarchical chunk tracking system, free queues, internal pool, and allocation zones.

Joe T. Sylve, Ph.D.