WD Purple 4TB (WD40PURZ) Surveillance Hard Drive – CMR, 64MB Cache for 24/7 DVR/NVR Recording (New)

Record every camera, every hour, without trusting your footage to a desktop drive.

The WD Purple 4TB (WD40PURZ) is a 3.5-inch CMR surveillance hard drive built for DVR and NVR security systems. It is designed for home users, small businesses and CCTV installers who need continuous recording, using AllFrame firmware and a 180TB/year workload rating to reduce dropped frames in 24/7 multi-camera setups.

Why Desktop Hard Drives Fail in DVR and NVR Recorders

Surveillance recording is the opposite of desktop use. A recorder writes video 24 hours a day, often from several cameras at once, inside a small enclosure with limited airflow. Desktop drives are built for short, read-heavy sessions. Under a constant write load they run hot, spend too long retrying difficult sectors and drop frames, and those problems usually show up only when you need to play back an incident.

The WD Purple 4TB is engineered for that workload. Its AllFrame firmware works with the ATA streaming commands DVRs and NVRs use, prioritizing a steady flow of video writes over lengthy recovery on a single sector, so a brief read issue costs a frame instead of stalling the recording. The drive is rated for 180TB/year of data transfer and 1,000,000 hours MTBF, figures built around always-on recorders rather than office PCs.

It also uses CMR (conventional magnetic recording), which writes each track independently. Write performance stays consistent when the recorder loops and overwrites old footage, and the 64MB cache with sustained transfer up to 150 MB/s keeps simultaneous camera streams flowing.

How Much Footage the WD Purple 4TB Stores

At Western Digital’s reference bitrate of 3.2 Mbps per camera (1080p, H.265, 25 fps), each camera writes roughly 35GB of video per day. On that basis, the WD Purple 4TB holds about 29 days of continuous footage from 4 cameras, or about 14 days from 8 cameras. Higher resolutions, higher frame rates and H.264 compression shorten that window; motion-based recording extends it.

Built for Heat, Vibration and Always-On Operation

The WD40PURZ is designed for recorders with up to 16 drive bays, where several drives spin side by side and share heat and vibration. Tarnish-resistant components help it cope with the humidity and temperature swings common in cabinets, closets and outdoor enclosures. Its 5400 RPM class spindle draws about 5.1 W on average during read/write, which keeps heat, noise and running costs low in a device that never switches off. It is rated to operate from 0°C to 65°C.

Setup Instructions

How to Install the WD Purple 4TB in Your DVR or NVR

1. Power down the recorder and unplug it before opening the case or a drive bay. Check its manual for the maximum supported capacity per drive.
2. Mount the drive in a free 3.5-inch bay or tray using the recorder’s screws or tool-less tray, then connect the SATA data and power cables.
3. Power on and open the storage or HDD menu. The new drive appears as uninitialized; initialize (format) it, noting that this erases any existing data.
4. Set your recording schedule, enable overwrite (loop recording) so the oldest footage is replaced automatically, and turn on HDD health or S.M.A.R.T. alerts.