WD Purple vs Red Plus: the 8TB numbers that differ (WD85PURZ vs WD80EFPX)

What the differences mean

Two different jobs: recorders up to 16 bays, NAS up to 8

Capacity, interface, cache, recording technology, workload rating, MTBF, noise and warranty are the same in both WD documents, so none of them decides between these two. What WD changes is the job. The datasheet states the Purple is a surveillance drive with AllFrame firmware, which WD describes as tuned for write-intensive, low bit-rate, high stream-count workloads. The Red Plus is a NAS drive with NASware, for RAID-optimized NAS systems. The bay counts are WD’s stated uses, not hardware limits: in a 12-bay chassis only the Purple stays inside its maker’s stated range.

Head parking: about 274 a day against 548

The datasheets rate the Purple for 300,000 load/unload cycles and the Red Plus for 600,000, the times the heads park and return. Spread over the 3-year warranty (1,095 days), that is about 274 a day for the Purple (300,000 ÷ 1,095) and 548 for the Red Plus (600,000 ÷ 1,095). A power-saving setting that parks the heads every five minutes, around the clock, uses 288 a day (1,440 minutes ÷ 5): above the Purple’s average, within the Red Plus’s. A recorder that writes continuously rarely parks; a NAS that sleeps between file requests can park often.

Idle power: about 11.4kWh a year per drive

The datasheets list 4.7 W at idle for the Purple and 3.4 W for the Red Plus. Idling around the clock, that is about 41.2kWh a year (4.7 W × 8,760 hours) against 29.8kWh (3.4 W × 8,760 hours): 11.4kWh a year per drive, 45.6kWh for four. In read/write the gap is 0.1 W (5.3 W against 5.2 W), under 1kWh a year. A recorder spends its day writing, so for the Purple the read/write figure is the one that counts.

The camera figure, turned into data

WD states the Purple supports up to 64 HD cameras, each a single 3.2Mbps stream. One such camera writes 0.4MB a second (3.2 ÷ 8), 34.56GB a day (0.4MB × 86,400 seconds), so an 8TB drive holds about 231 days of one camera (8,000GB ÷ 34.56GB). All 64 together write 25.6MB a second, about 12% of the 215MB/s figure, and 2.21TB a day: about 3.6 days of footage on one drive. The 180TB/year rating is about 493GB a day (180TB ÷ 365), which covers about 14 of those cameras recording 24/7 to a single drive (493 ÷ 34.56). WD doesn’t say how the 64 cameras split across the drives of a recorder: the camera count is a stream figure, the workload rating a yearly data budget. The Red Plus brief gives no camera figure.

Same 215MB/s, two definitions

Both datasheets print 215MB/s, but under the two definitions in the table above: equal numbers under different definitions don’t prove equal speed. The Red Plus brief adds a rotational speed of 5640 RPM; the Purple data sheet gives none, so this page doesn’t compare one.

Features one datasheet names and the other doesn’t

The Purple data sheet lists RV sensors, RAID error recovery control and tarnish-resistant components; the Red Plus brief names dual-plane balance control and an Air drive. Neither document mentions the other’s features, which is not the same as a drive lacking them: treat these as WD’s descriptions, not as confirmed differences.