Here is the short answer: buy days, not terabytes. For a typical four-camera 5MP system recording a sensible mix of motion and continuous, 2TB holds roughly a fortnight and 4TB roughly a month — and the drive must be one made for CCTV duty, because a recorder writes around the clock and an ordinary desktop drive is not built for that life.
Storage is the part of a CCTV system nobody thinks about until the week they need footage from eleven days ago and the recorder only holds nine. The camera adverts talk about megapixels; the thing that decides whether you have evidence is the disc.
We have specced recorders from the Villa Road counter since 1975, and the same three mistakes walk in every month: too small a drive, the wrong kind of drive, and continuous recording on cameras that watch an empty drive all day.
1. The only number that matters is days retained
Ask one question of any system: if something happened while I was on a fortnight's holiday, would the footage still be there when I got back? A fortnight is the sensible floor for a home; many businesses want a month. Whatever you decide, decide it in days — then buy the terabytes that deliver it.
2. What eats storage
- Resolution: the big one. Doubling detail multiplies data — a 4K stream fills a disc far faster than a 5MP one, which is one of the quiet costs of buying more camera than the job needs.
- Number of cameras: linear and unavoidable. Eight cameras eat twice what four do.
- Continuous vs motion recording: the lever you control. Continuous on every channel fills the disc with an empty driveway.
- Frame rate and encoding: modern recorders compress well; ancient settings waste discs. If a recorder is years old, its settings deserve an hour before its drive gets replaced.
Trade tip: the mix experienced installers actually use — continuous on the doors, motion on the road-facing and rarely-troubled views. It keeps the pre-event seconds where they matter and can stretch the same drive to double the retained days.
3. A working sizing guide
Working rules from the counter, for a sensible motion-and-continuous mix — your recorder's own calculator gives the exact figure for your settings:
| System | 1TB | 2TB | 4TB |
|---|---|---|---|
| 2 × 5MP cameras | ~2 weeks | ~1 month | 2 months+ |
| 4 × 5MP cameras | ~1 week | ~2 weeks | ~1 month |
| 4 × 4K cameras | days | ~1 week | ~2 weeks |
Read that 4K row twice before buying 4K everywhere — and if you are weighing resolutions, our guide to what makes a good 4K CCTV system covers where the extra pixels earn their storage.
4. Surveillance drives are not marketing
A desktop drive is designed for bursts of reading; a CCTV recorder writes continuously, around the clock, often from several streams at once. Surveillance-rated drives are built and firmware-tuned for exactly that duty, which is why the failure story we hear — "the recorder was working, but when we needed the footage the disc had died" — so often ends with a desktop drive being pulled out of the caddy.
The ESP HD2000SA 2TB is our stocked CCTV drive at the fortnight-for-four-cameras size, with the HD1000SA 1TB for smaller two-camera systems. Both are supplied for CCTV recorder duty — fit, format in the recorder, done.
Standalone and solar 4G cameras record to a card instead of a recorder — the Hikvision 512GB microSDXC is the right shape for those, and card endurance matters for exactly the same always-writing reason.
5. The recorder half of the question
Retention is set by drive and recorder together. The Hikvision 16-channel AcuSense PoE NVR is the kind of platform that helps on both ends: PoE for the cameras down one cable each, and AcuSense classification meaning motion events are real events — which is retention you don't waste. If you are still deciding between recorder families, read NVR vs DVR first; it constrains every later choice.
6. The law and the overwrite
CCTV storage loops: when the disc fills, the oldest footage goes. For a home that is fine — but if your cameras take in anything beyond your own boundary, retention becomes part of your data responsibilities, and businesses should hold footage no longer than they can justify. Our guide to CCTV rules and regulations in the UK covers it properly.
Expert Help in the West Midlands
Villa Road, Birmingham, since 1975. Tell us the camera count, the resolutions and the days you want to keep, and we will size the drive at the counter — and tell you honestly when the cheaper fix is a settings change, not a bigger disc.
Browse CCTV hard drives and storage, network video recorders and digital video recorders. Get in touch for a spec.
Frequently Asked Questions
How much storage do I need for CCTV?
Decide the days first — a fortnight minimum for a home — then size the disc: as a working rule, 2TB holds roughly two weeks for a four-camera 5MP system on sensible settings, and 4K roughly halves whatever you were expecting.
Can I use a normal hard drive in a CCTV recorder?
It will work — until it matters. Recorders write continuously and surveillance-rated drives are built for that duty; desktop drives are the most common cause of the footage being gone when it is finally needed.
How long does CCTV footage last before it is overwritten?
Until the disc is full, then the oldest goes first. That is why the honest answer to "how long is footage kept" is whatever your drive size and settings deliver — measure it once in the recorder and check it holds the fortnight.