Western Digital WD Black SN7100 4TB VS Western Digital WD Black SN8100 1TB

Read speed is where these two drives diverge most dramatically. The SN8100 1TB posts a sequential read speed of 14900 MB/s, more than double the 7250 MB/s of the SN7100 4TB. In practical terms, this gap is felt most acutely when transferring large files — think massive video project assets, disk images, or game installations — where the SN8100 can sustain roughly twice the throughput, cutting transfer times nearly in half compared to the SN7100.

The random read performance tells a similar story. The SN8100 reaches 1,600,000 IOPS versus the SN7100's 900,000 IOPS — a roughly 78% advantage. Random IOPS matter most in workloads involving many small, unpredictable reads, such as booting an OS, launching applications, or running a database. For a power user or professional dealing with these access patterns, the SN8100's lead here is not marginal — it is substantial.

The SN8100 1TB holds a clear and decisive edge in this category across both sequential and random read metrics. The SN7100 4TB trades read performance for significantly higher storage capacity, making it the better fit for users prioritizing space over speed — but strictly on read performance, the SN8100 is the stronger drive.

Write performance follows the same pattern established by the read specs. The SN8100 1TB achieves a sequential write speed of 11000 MB/s, compared to 6900 MB/s for the SN7100 4TB — roughly a 60% advantage. For content creators exporting large video files, developers writing hefty build artifacts, or anyone doing regular large-scale backups, that gap translates directly into faster completion times and less time waiting on storage.

On the random write side, the SN8100 extends its lead further, hitting 2,400,000 IOPS against the SN7100's 1,350,000 IOPS — a 78% difference. Random write performance is particularly relevant for database transactions, virtual machine activity, and system-intensive multitasking where small writes are continuously queued. At this level of IOPS separation, the SN8100 would handle sustained mixed workloads noticeably more fluidly.

Across both sequential and random write metrics, the SN8100 1TB wins this category convincingly. Users whose workflows are write-heavy — video editing, software development, or virtualization — will feel the difference meaningfully. The SN7100 4TB remains competitive in absolute terms, but it cannot match the SN8100's write throughput at any level of this comparison.

The architectural gap between these two drives starts at the interface level. The SN8100 1TB runs on PCIe 5.0 with NVMe 2.0, while the SN7100 4TB operates over PCIe 4.0 with NVMe 1.4. This generational difference is the root cause of the dramatic speed disparities seen in read and write performance — PCIe 5.0 doubles the available bandwidth ceiling compared to PCIe 4.0. Pairing that with a doubling of controller channels (8 vs 4) means the SN8100 can parallelize data operations far more aggressively, which compounds the throughput advantage.

Caching architecture is another meaningful differentiator. The SN8100 uses a dedicated DRAM cache, which provides fast, consistent low-latency buffering independent of system resources. The SN7100 relies on HMB (Host Memory Buffer), borrowing a slice of system RAM instead. HMB is a reasonable cost-saving approach and works well in typical consumer workloads, but dedicated DRAM is more predictable under sustained loads and mixed I/O pressure — an advantage in professional or server-adjacent use cases.

Where the SN7100 4TB reasserts itself is in capacity and endurance. Its 4TB of storage dwarfs the SN8100's 1TB, and its 2400 TBW endurance rating reflects the longevity expected of a higher-capacity drive. Both carry identical 5-year warranties and use TLC NAND. Overall, the SN8100 wins on architecture and raw capability, while the SN7100 is the stronger choice for users who need maximum storage space and long-term write endurance.