How long does it take to write 100 GB to a Gen4 NVMe SSD? Cache and cooling limits

How this is calculated

Real-world Gen4 NVMe sustained write performance drops sharply once the drive's SLC cache fills, typically after 50-150 GB written depending on drive capacity. A 1 TB 980 Pro holds the full 7 GB/s for about the first 100 GB, then drops to roughly 1.6 GB/s native TLC speed, extending the 100 GB transfer to more like 40-50 seconds if the cache is already partly used. PCIe 5.0 NVMe doubles the peak to ~14 GB/s, cutting this to 7 seconds under ideal conditions.

Verdict

100 GB to a PCIe 4.0 NVMe SSD at the interface's ~7 GB/s (56 Gbps) peak works out to 14 seconds, the fastest consumer-storage transfer you can do and the benchmark speed to compare portable and external drives against when evaluating their real performance. The 14-second figure is the best case on a fresh sequential write to a healthy drive, while sustained workloads with thermal throttling or random IO drop the real-world rate to ~3-4 GB/s. That's what makes the jump from SATA SSD (3 minutes for the same 100 GB at 550 MB/s) to NVMe transformative for large-file workflows is the ~12-13x throughput gap, which is the gap that shifts large video projects, model weights, and backup clones from minutes-per-terabyte to seconds-per-terabyte on the data path.