Overview
- This week multiple hands-on tests and teardowns found Apple fitted the 1TB and 2TB iPhone 18 Pro/Pro Max models with QLC flash while 256GB and 512GB variants use faster TLC.
- Bilibili tester HOMOLAB measured the 1TB QLC unit sustaining about 79 MB/s on prolonged writes, with occasional dips to 25.6 MB/s and isolated minima reported near 1.1 MB/s in extreme synthetic runs.
- Apple’s storage uses a tiered write path: a small fast SLC cache (thousands of MB/s), a slower pseudo‑TLC buffer (hundreds of MB/s), then direct QLC writes that are much slower once those caches fill.
- Available free space strongly reduces cache headroom; HOMOLAB showed that filling a phone to roughly 60% shrank the SLC cache and pushed sustained QLC writes down to averages near 45 MB/s with brief near‑1 MB/s lows.
- Everyday users are unlikely to see these worst cases, but professionals doing long high‑bitrate ProRes recording, very large file transfers, or full backup restores may encounter noticeable slowdowns because those tasks can exhaust the caches.