Samsung 990 EVO Plus 4TB vs Western Digital WD_BLACK SN850X 4TB
Western Digital WD_BLACK SN850X 4TB is at least the equal of the other on every measure that decides this, and ahead on at least one.
| Specification | Samsung990 EVO Plus 4TB | Western DigitalWD_BLACK SN850X 4TB |
|---|---|---|
| Capacity (GB) | 4000 | 4000 |
| Sequential read (MB/s) | 7250 | 7300better |
| Sequential write (MB/s) | 6300 | 6600better |
| Current best price | $1,000.59at Amazon.ca · captured 2026-09-13 | $829.99betterat Amazon.ca · captured 2026-09-13 |
| Price per TB | $250.15 | $207.50better |
| Endurance (TBW) | 2400 | 2400 |
| Warranty (years) | 5 | 5 |
| DRAM cache | No | Yes |
| NAND type | tlc | tlc |
| Controller | Samsung in-house controller | Western Digital in-house 8-channel controller |
How these two compare
Sequential throughput
Samsung 990 EVO Plus 4TB states 7250 MB/s read and 6300 MB/s write; Western Digital WD_BLACK SN850X 4TB states 7300 MB/s read and 6600 MB/s write, both over PCIe. Sequential numbers like these describe large sustained transfers; the responsiveness you notice day to day tracks random access more closely than the peak figures do.
Random access
Samsung 990 EVO Plus 4TB is rated 1,050,000 IOPS random read and 1,400,000 random write; Western Digital WD_BLACK SN850X 4TB, 1,200,000 and 1,100,000. Random 4K access — many small, scattered operations — is what a drive does booting, launching apps and juggling everyday tasks, and it tracks that feel far more closely than the sequential figures above.
Price
Samsung 990 EVO Plus 4TB is $1,000.59 ($250.15 per TB); Western Digital WD_BLACK SN850X 4TB is $829.99 ($207.50 per TB).
Endurance
Samsung 990 EVO Plus 4TB is rated for 2400 TBW and Western Digital WD_BLACK SN850X 4TB for 2400 TBW — the total the maker warrants you can write over the drive's life. A typical desktop writes only a few terabytes a year, so either rating is many years of headroom; the figure matters mainly as a relative signal of how hard each is built to be driven.
DRAM cache
On the cache question: Samsung 990 EVO Plus 4TB is DRAM-less, and Western Digital WD_BLACK SN850X 4TB carries a DRAM cache. The DRAM keeps the flash-translation table close, sparing a lookup on nearly every access; a drive without it leans on host memory or its own flash, which usually shows as slower sustained random writes rather than in the headline sequential numbers.
NAND, controller and warranty
On the flash itself: Samsung 990 EVO Plus 4TB uses TLC, and Western Digital WD_BLACK SN850X 4TB uses TLC. NAND tiers count bits per cell — more bits pack more capacity into the same silicon but shorten write endurance and slow sustained writes, which is why QLC sits below TLC on lasting performance even when the sequential numbers match. Controller: Samsung 990 EVO Plus 4TB uses the Samsung in-house controller and Western Digital WD_BLACK SN850X 4TB uses the Western Digital in-house 8-channel controller. The controller runs wear-levelling, error correction and the mapping table, so it shapes sustained and random behaviour as much as the flash does — though the model name alone predicts little without testing. Samsung 990 EVO Plus 4TB carries a 5-year warranty and Western Digital WD_BLACK SN850X 4TB carries a 5-year warranty — the length the maker will stand behind the drive, and usually a proxy for the endurance it is rated to.
Which to buy
Against the other, Western Digital WD_BLACK SN850X 4TB is even or ahead on every tracked measure and behind on none, which is the one case where the choice needs no compromise.
Common questions about this pair
- Which is faster, Samsung 990 EVO Plus 4TB or Western Digital WD_BLACK SN850X 4TB?
- Samsung 990 EVO Plus 4TB states 7250 MB/s read and 6300 MB/s write; Western Digital WD_BLACK SN850X 4TB states 7300 MB/s read and 6600 MB/s write, both over PCIe. Sequential numbers like these describe large sustained transfers; the responsiveness you notice day to day tracks random access more closely than the peak figures do.
- How do Samsung 990 EVO Plus 4TB and Western Digital WD_BLACK SN850X 4TB compare on random access?
- Samsung 990 EVO Plus 4TB is rated 1,050,000 IOPS random read and 1,400,000 random write; Western Digital WD_BLACK SN850X 4TB, 1,200,000 and 1,100,000. Random 4K access — many small, scattered operations — is what a drive does booting, launching apps and juggling everyday tasks, and it tracks that feel far more closely than the sequential figures above.
- Which costs less per terabyte, Samsung 990 EVO Plus 4TB or Western Digital WD_BLACK SN850X 4TB?
- Samsung 990 EVO Plus 4TB is $1,000.59 ($250.15 per TB); Western Digital WD_BLACK SN850X 4TB is $829.99 ($207.50 per TB).
- Should you buy Samsung 990 EVO Plus 4TB or Western Digital WD_BLACK SN850X 4TB?
- Against the other, Western Digital WD_BLACK SN850X 4TB is even or ahead on every tracked measure and behind on none, which is the one case where the choice needs no compromise.