WD Red SN700 - M.2 PCIe Gen3 NVMe SSD - 4TB

The WD Red SN700 is WD's NVMe SSD designed for NAS caching workloads. Built on a custom SanDisk controller with dedicated DDR4 DRAM cache and Kioxia 96-layer BiCS4 TLC NAND. Sequential reads reach 3,430 MB/s over PCIe Gen 3 x4. Available from 250GB to 4TB.

NAS Caching

The primary use case is as a read/write cache in NAS devices that support NVMe caching (Synology, QNAP, TrueNAS). The DRAM cache and high endurance rating make it suitable for the mixed random I/O patterns that NAS caching generates. It also works as a standard NVMe boot or storage drive.

DRAM Cache

Unlike WD's consumer NVMe drives (SN770, SN7100, Blue SN5000), the Red SN700 includes a dedicated DDR4 DRAM cache. This is important for NAS caching where random I/O consistency matters more than peak sequential throughput.

Endurance

Endurance ratings are significantly higher than consumer drives, reflecting the expected write-heavy NAS caching workload:

Capacity	TBW	TBW per TB
250GB	500	2,000
500GB	1,000	2,000
1TB	2,000	2,000
2TB	2,500	1,250
4TB	5,100	1,275

The 250GB through 1TB models deliver 2,000 TBW per TB, roughly 3x higher than consumer NVMe drives. Backed by a 5-year warranty and 1.75 million hour MTTF.

PCIe Gen 3

The SN700 uses PCIe Gen 3, not Gen 4. For NAS caching, this is rarely a bottleneck since the workload is random I/O (where IOPS matter more than sequential bandwidth) and the NAS itself is limited by network throughput.

Best for: NAS caching in Synology, QNAP, or TrueNAS builds; write-heavy workloads that need high endurance.

Avoid if: You need maximum sequential speed for direct storage use (the Gen 3 interface caps throughput below what Gen 4 drives deliver).