WD_BLACK 4TB SN850P

WD_BLACK 4TB SN850P Review & Specifications

The WD_BLACK 4TB SN850P by Sandisk Technologies, Inc. is a NVMe solid-state drive (SSD) featuring 4000 GB of storage. It is built with None NAND flash memory and utilizes a None controller to manage data access, wear leveling, and overall performance. This drive runs on the PCIe 4.0 x4 interface (up to 16 GB/s) and utilizes the NVMe 1.4 protocol. NVMe 1.4 brought significant updates such as improved power management, persistent memory region support, and native command retry. The SSD comes in a M.2 2280 form factor. PCIe 4.0 is backward compatible with older PCIe slots, but speeds will adjust accordingly.

NVMe SSD Performance

Sequential read and write speeds reach 7300 MB/s and 6300 MB/s respectively, while random read/write performance delivers up to 1200k and 1100k IOPS. The drive offers an endurance rating of 2400 TBW and is backed by a 5-year manufacturer warranty.

This SSD does not include a dedicated external DRAM cache chip. Instead, it relies on a small internal SRAM cache integrated into the controller, typically around 32 MB to 128 MB. Manufacturers may sometimes refer to this SRAM as "DRAM cache," but it is not the same as a discrete DRAM module. Furthermore, because it uses the NVMe interface, the SSD may also support Host Memory Buffer (HMB) — a feature that allocates a small portion of your system’s RAM (usually 64–128 MB) to act as a substitute for DRAM. While this design is cost-effective and suitable for everyday tasks, performance under heavy or sustained random I/O can be lower compared to full-DRAM SSDs. A Dynamic SLC cache is still included to help with write bursts and improve responsiveness.

This SSD module provides strong mid-range performance, achieving 71.2% of the highest score in our benchmark. It delivers excellent responsiveness and load times for a wide variety of tasks, making it ideal for mainstream gaming setups, content creation, software development, and multitasking-oriented workflows. Unless you're working with large-scale real-time data or intensive write-heavy workloads, this level of performance is more than sufficient for demanding users.

Cost-Effectiveness

From a cost-per-storage perspective, this SSD offers below-average value at $195.0 per terabyte. The overall combined performance-to-price ratio, which evaluates both maximum performance and total storage capacity per dollar, is calculated at 54.8%. Based on this metric, the drive is a less favorable value in this category. Considering its performance rating of 71.2%, other SSDs at similar or lower prices may deliver better overall performance and capacity per dollar, making this drive less competitive.