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TechFading · day 3

iPhone 18 Pro Max's 1TB storage hits 1.1 MB/s under sustained heavy writes

Bilibili testing reveals Apple's QLC flash storage in the high-capacity model drops to hard-drive speeds once its cache is exhausted.

newest coverage 4h agosummary written 2d ago4 pieces6 likes & upvotes Hacker NewsMastodonNewswires

What to know

  • Apple's use of QLC flash storage in the 1TB iPhone 18 Pro Max allows higher capacity but introduces significant performance trade-offs: sustained write speeds can drop to 1.1–45 MB/s once cache buffers are exhausted, slower than budget microSD cards.
  • The performance gap is most acute under sustained heavy workloads (4K/ProRes recording, large file transfers, backups), which are exactly the use cases high-capacity buyers are likely to undertake.
  • Storage degradation worsens as the drive fills: available cache shrinks from ~250GB to 58GB at 60% capacity, further reducing write performance.
  • Most everyday users (texting, browsing, casual photos) will not notice the slowdown; impact is limited to specific intensive tasks.
some voices

This is an acceptable trade-off for users who need the 1TB capacity and understand the performance cost.

  • “For most everyday tasks—texting, browsing, and taking casual photos—this likely won't be noticeable, since the cache handles typical bursts well.”

    Notebook Check · Hacker News ↗

“While both storage types perform fairly similarly in 4K read tests, the QLC model falls behind by 38% in a low-queue-depth mixed workload, scoring 8,168 compared to 11,285 for the TLC model.”

Tom's Hardware · Tom's Hardware ↗

Apple Device manufacturerHOMOLAB Testing lab (Bilibili channel)

iPhone 18 Pro Max's 1TB storage hits 1.1 MB/s under sustained heavy writes
Tom's Hardware

How it unfolded 2 developments, newest first · click a bar or a number to jump articlesposts

Peak 1 piece in one hour at Sep 21, 1 AM; 4 pieces over 3 days (1 article · 3 posts) Sep 21, 1 AM — 1 piece · 1 post — Hacker News 1Sep 21, 2 AM — quietSep 21, 3 AM — quietSep 21, 4 AM — quietSep 21, 5 AM — quietSep 21, 6 AM — quietSep 21, 7 AM — 1 piece · 1 post — Mastodon 1Sep 21, 8 AM — quietSep 21, 9 AM — quietSep 21, 10 AM — quietSep 21, 11 AM — quietSep 21, 12 PM — 1 piece · 1 article — Newswires 1Sep 21, 1 PM — quietSep 21, 2 PM — quietSep 21, 3 PM — quietSep 21, 4 PM — quietSep 21, 5 PM — quietSep 21, 6 PM — quietSep 21, 7 PM — quietSep 21, 8 PM — quietSep 21, 9 PM — quietSep 21, 10 PM — quietSep 21, 11 PM — quietSep 22, 12 AM — quietSep 22, 1 AM — quietSep 22, 2 AM — quietSep 22, 3 AM — quietSep 22, 4 AM — quietSep 22, 5 AM — quietSep 22, 6 AM — quietSep 22, 7 AM — quietSep 22, 8 AM — quietSep 22, 9 AM — quietSep 22, 10 AM — quietSep 22, 11 AM — quietSep 22, 12 PM — quietSep 22, 1 PM — quietSep 22, 2 PM — quietSep 22, 3 PM — quietSep 22, 4 PM — quietSep 22, 5 PM — quietSep 22, 6 PM — quietSep 22, 7 PM — quietSep 22, 8 PM — quietSep 22, 9 PM — quietSep 22, 10 PM — quietSep 22, 11 PM — quietYesterday, 12 AM — quietYesterday, 1 AM — quietYesterday, 2 AM — quietYesterday, 3 AM — quietYesterday, 4 AM — quietYesterday, 5 AM — quietYesterday, 6 AM — quietYesterday, 7 AM — quietYesterday, 8 AM — quietYesterday, 9 AM — quietYesterday, 10 AM — quietYesterday, 11 AM — quietYesterday, 12 PM — quietYesterday, 1 PM — quietYesterday, 2 PM — quietYesterday, 3 PM — quietYesterday, 4 PM — quietYesterday, 5 PM — quietYesterday, 6 PM — quietYesterday, 7 PM — 1 piece · 1 post — Hacker News 1Yesterday, 8 PM — quietYesterday, 9 PM — quietYesterday, 10 PM — quietYesterday, 11 PM — quiet 1–2
Sep 22yesterdaynow · 12:58 AM ET
  1. 1

    Coverage contextualizes findings as worst-case scenario; impact limited to intensive tasks

    Multiple outlets report that HOMOLAB's benchmarks represent synthetic, worst-case conditions unlikely to affect typical users during everyday tasks like texting, browsing, or casual photography. Slowdowns become apparent only during sustained intensive workloads such as 4K or ProRes video recording, large file transfers, or backup restores—use cases that high-capacity buyers are most likely to encounter.

    • appleinsider@mastodon.social

      The storage of the iPhone 18 Pro Max can run at very slow speeds, but only under artificially extreme, sustained loads. Most consumers won't experience this at all. https:// appleinsider.com/articles/26/0 9/21/iphone-18-pro-max-storage-hits-glacial-speeds-under-extreme-loads?utm_medium=social&utm_source=mastodon

      appleinsider@mastodon.socialMastodon2d agoview on Mastodon ↗
  2. background

    Performance gap worsens as storage fills to 60% capacity — HOMOLAB's testing shows that as the iPhone 18 Pro Max's drive fills, the available SLC cache drops sharply from approximately 250GB to just 58GB, reducing the device's ability to absorb write bursts. The secondary TLC-simulating buffer slows from 578 MB/s to 396 MB/s, while direct QLC writes average just 45 MB/s and occasionally drop to 1.1 MB/s—well behind competing TLC-based storage in other flagship phones.

  3. 2

    HOMOLAB benchmarks iPhone 18 Pro Max 1TB storage under sustained heavy loads

    Bilibili channel HOMOLAB tested the iPhone 18 Pro Max with 1TB QLC storage against the 512GB TLC model and found performance degradation under sustained writes. The QLC model lags the TLC model by 38% in low-queue-depth mixed workloads (8,168 vs 11,285) and maintains roughly 12% slower performance under heavier loads. Once the phone's fast SLC cache is exhausted, sustained write speeds drop to 79.4 MB/s on average, bottoming out at 25.6 MB/s—slower than many budget microSD cards.

    “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.”
    — HOMOLAB

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