Interface: ST18000NM001J lists SATA 6 Gb/s; WD181KFGX lists SATA 6Gb/s.
Cache (MB): ST18000NM001J lists 256; WD181KFGX lists 512.
Sustained transfer (up to MB/s): ST18000NM001J lists 270; WD181KFGX lists 272.

A larger cache, higher RPM or higher advertised sequential speed alone does not establish which drive is better for your workload.

Specifications side by side

Show differences only

Manufacturer specifications for ST18000NM001J and WD181KFGX
Specification	ST18000NM001J	WD181KFGX
Manufacturer	Seagate	Western Digital
Product family	Exos X18	WD Red Pro
Model number	ST18000NM001J	WD181KFGX
Capacity (TB)	18	18
RPM	7200	7200
Interface	SATA 6 Gb/s	SATA 6Gb/s
Cache (MB)	256	512
Form factor	3.5-inch	3.5-inch
Average idle power (W)	5.3	Not recorded
Power-on hours per year	8760	Not recorded
Manufacturer limited warranty	5 years (eligible new drives)	5 years (eligible new drives)
Sustained transfer (up to MB/s)	270	272
Recording	Not recorded	CMR
Workload rating (TB/year)	Not recorded	550
Physical sector size (bytes)	Not recorded	4096

Compatibility and buying checks

Compare new and renewed offers separately. The manufacturer specification does not guarantee the warranty or return policy of a marketplace seller.

Reviewed 2026-09-07. Published specifications; no independent benchmark or failure-rate claim.

Reviewed 2026-08-21. Published specifications; no independent benchmark or failure-rate claim.