GoKawiil1TB iPhone 18 Pro Max's QLC storage slows to 1.1 MB/s under heavy write loads
Testing by Bilibili channel Homolab found that the 1TB iPhone 18 Pro Max, which uses QLC NAND, suffers major performance drops compared to the 512GB TLC-based iPhone 18 Pro. Once its SLC and secondary TLC caches are exhausted, sustained writes fall to about 79.4 MB/s and can dip as low as 25.6 MB/s, worsening to just 1.1 MB/s once the drive is 60% full.