Verdict

For a NAS cache or write-heavy pool, the WDS400T2X0E is the safer pick - the WDS400T4B0E uses QLC NAND, which wears out faster and slows badly under sustained writes (light, read-mostly use only).

WDS400T2X0E
WD Black SN850X · 4TB · Desktop
No FR price yet
WDS400T4B0E
WD Blue SN5000 · 4TB · Desktop
€497 (€124.35/TB)

Value at a glance

Price / TB
WDS400T2X0E $197.50
WDS400T4B0E $116.74
Endurance (TBW)
WDS400T2X0E 2,400 TB
WDS400T4B0E 1,200 TB

Price history

FR · cheapest per day

WDS400T4B0E €497
zoomed · drag to zoom
€540 €376 €213 Nov 2024 Mar 2025 Aug 2025 Jan 2026 Jun 2026 Nov 2026
WDS400T2X0E WDS400T4B0E
Capacity 4 TB 4 TB
Form factor M.2 M.2
Interface NVMe NVMe
NAND type TLC QLC
Endurance (TBW) 2,400 TB 1,200 TB
DWPD - -
DRAM cache Yes No
Power-loss protection No No
Sustained write - -
Cost / TBW $0.329 $0.389
Price / TB $197.50 $116.74
Buy No FR price yet
€497
View at Amazon →

Highlighted cells mark the stronger spec for a NAS build. Failure rates from Backblaze Drive Stats where available; $/TB uses the cheapest live price. Buy links are Amazon affiliate.

WDS400T2X0E

No Backblaze failure data for this model.

WDS400T4B0E

No Backblaze failure data for this model.