SanDisk Optimus GX PRO 850X 4TB vs Western Digital WD_BLACK SN850P 4TB
Western Digital WD_BLACK SN850P 4TB is at least the equal of the other on every measure that decides this, and ahead on at least one.
| Specification | SanDiskOptimus GX PRO 850X 4TB | Western DigitalWD_BLACK SN850P 4TB |
|---|---|---|
| Capacity (GB) | 4000 | 4000 |
| Sequential read (MB/s) | 7300 | 7300 |
| Sequential write (MB/s) | 6600 | 6600 |
| Current best price | $990.00at Newegg · captured 2026-09-11 | $868.00betterat Newegg · captured 2026-09-04 |
| Price per TB | $247.50 | $217.00better |
| DRAM cache | Yes | Yes |
| NAND type | tlc | tlc |
How these two compare
Sequential throughput
SanDisk Optimus GX PRO 850X 4TB states 7300 MB/s read and 6600 MB/s write; Western Digital WD_BLACK SN850P 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.
Price
SanDisk Optimus GX PRO 850X 4TB is $990.00 ($247.50 per TB); Western Digital WD_BLACK SN850P 4TB is $868.00 ($217.00 per TB).
DRAM cache
On the cache question: SanDisk Optimus GX PRO 850X 4TB carries a DRAM cache, and Western Digital WD_BLACK SN850P 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
On the flash itself: SanDisk Optimus GX PRO 850X 4TB uses TLC, and Western Digital WD_BLACK SN850P 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.
Which to buy
Against the other, Western Digital WD_BLACK SN850P 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, SanDisk Optimus GX PRO 850X 4TB or Western Digital WD_BLACK SN850P 4TB?
- SanDisk Optimus GX PRO 850X 4TB states 7300 MB/s read and 6600 MB/s write; Western Digital WD_BLACK SN850P 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.
- Which costs less per terabyte, SanDisk Optimus GX PRO 850X 4TB or Western Digital WD_BLACK SN850P 4TB?
- SanDisk Optimus GX PRO 850X 4TB is $990.00 ($247.50 per TB); Western Digital WD_BLACK SN850P 4TB is $868.00 ($217.00 per TB).
- Should you buy SanDisk Optimus GX PRO 850X 4TB or Western Digital WD_BLACK SN850P 4TB?
- Against the other, Western Digital WD_BLACK SN850P 4TB is even or ahead on every tracked measure and behind on none, which is the one case where the choice needs no compromise.