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. Samsung rates the 1 TB 980 Pro for up to 7,000 MB/s sequential read and 5,000 MB/s sequential write, so 100 GB at the rated write speed is about 20 seconds before overhead. A partly used cache, thermal throttling, or a fuller drive can extend the transfer to roughly 40-60 seconds. PCIe 5.0 NVMe doubles the interface peak to ~14 GB/s, cutting the ideal interface math to 7 seconds.

Verdict

The PCIe 4.0 interface's ~7 GB/s (56 Gbps) ceiling puts 100 GB at 14 seconds in ideal math. A Samsung 980 Pro 1 TB is rated for up to 7,000 MB/s sequential reads and 5,000 MB/s sequential writes, so its rated write-speed math is about 20 seconds before overhead. Sustained workloads can be slower because of SLC cache exhaustion, thermal throttling, drive fill level, or random IO. That is still a large jump from a SATA SSD, which takes about 3 minutes for the same 100 GB at 550 MB/s.