“Once that cache is exhausted, the phone falls back to a secondary buffer that simulates TLC-like storage and remains faster than raw QLC, averaging 578 MB/s but exhibiting substantial variation. Only after that secondary buffer is also exhausted does the phone write directly to raw QLC storage, where HOMOLAB measured sustained speeds dropping to an average of just 79.4 MB/s.”

Notebook Check (via Hacker News) · iPhone 18 Pro Max's 1TB storage hits 1.1 MB/s under sustained heavy writes

“At 60% capacity, the reduced free space leaves less room for the fast cache, and the available SLC cache drops sharply from around 250GB on an empty drive to just 58GB.”

Notebook Check (via Hacker News) · iPhone 18 Pro Max's 1TB storage hits 1.1 MB/s under sustained heavy writes