A surveillance hard drive is the part of a CCTV system people think about last and regret first. Ordinary desktop drives are built to spin for a few hours a day; a CCTV recorder writes to its drive every second of every day, from every camera at once. Surveillance-rated drives — WD Purple and Toshiba S300 — are designed for that continuous write load and for the ATA streaming commands recorders use, which is why they last where a standard drive drops frames or fails inside a year.

How much storage do I actually need?

Work it out from your cameras, not from the drive sizes on offer. As a rough guide, a single camera recording continuously in H.265 uses roughly:

So four 4MP cameras recording continuously for 14 days need roughly 2.4TB — a 4TB drive with headroom. Eight 4MP cameras for 30 days is closer to 10TB, which means an 8TB drive and shorter retention, or a two-bay recorder. Two things reduce these figures substantially in practice: recording on motion or AcuSense person/vehicle events rather than continuously, and letting the recorder drop to a lower sub-stream bitrate when nothing is happening. Treat the table as a ceiling and size up rather than down — a drive that fills early simply overwrites your oldest footage, which is exactly the footage you tend to need.

Want an exact figure for your own setup? Use our CCTV storage calculator — enter your camera count, resolution and retention period and it will recommend the WD Purple or Toshiba S300 drive that fits.

Choosing the right drive

• Match the bay count, not just the capacity. Most 4- and 8-channel NVRs and DVRs take one 3.5in SATA drive. Check the recorder’s maximum supported capacity before buying an 8TB or larger drive — older units cap out below that.
• Surveillance-rated only. WD Purple and Toshiba S300 are built for 24/7 write cycles and multi-camera streams. Desktop Blue/Green drives are not, and using one usually voids the sensible warranty conversation.
• More cameras needs a higher-tier drive. The larger WD Purple and Purple Pro capacities support more simultaneous streams, which matters once you pass roughly 16 cameras.
• Buy the drive with the system. Fitting it at install takes minutes; retro-fitting later means taking the recorder off the wall and losing whatever it recorded in the meantime.

Fitting and compatibility

Every drive here is a standard 3.5in SATA unit and works in HiLook and Hikvision NVRs, HD-TVI DVRs and Dahua recorders. Fit it before first power-up where you can: the recorder will prompt you to initialise the drive, and it needs formatting in the recorder itself rather than on a PC. Recorders sold as part of our CCTV kits can be supplied with a drive already fitted.

Not sure which recorder you are pairing it with? Our guide to choosing a HiLook NVR covers channel counts and bay counts, and if you would rather talk it through, our Wolverhampton counter and showroom is open six days a week — see CCTV in Wolverhampton.