CCTV Hard Drive Guide 2026: Size & Capacity

Guessing your CCTV storage and hoping for the best is how UK installers end up with systems that silently stop recording three weeks before someone actually needs the footage. Get the sizing right from the start — camera count, resolution and retention days, run through a purpose-built surveillance drive like the Seagate SkyHawk 4TB or Toshiba S300 Pro 10TB — and you'll never be caught explaining a gap in the evidence trail. This guide gives you the maths, the drive types, and the backup logic to get it right first time.

Which Hard Drive for CCTV? A UK Storage & Capacity Guide

Size a CCTV hard drive by multiplying your cameras' combined daily bitrate by the number of retention days, not by picking a round number off the shelf. A single 4MP camera recording continuously at a moderate bitrate can eat through several hundred gigabytes a week, so an 8-camera system holding 30 days typically needs somewhere in the 4TB–10TB range depending on resolution, frame rate and how much motion-only recording you use.

Surveillance HDD vs desktop HDD

A surveillance drive is built for sustained 24/7 sequential writes across multiple simultaneous camera streams; a desktop drive is built for occasional, bursty reads and isn't rated for that duty cycle. The Seagate SkyHawk 4TB is explicitly designed for multi-camera DVR/NVR workloads, running at 5900RPM and priced at £102.35 from cctvmaster.co.uk. Toshiba's surveillance line takes a different route: the Toshiba S300 4TB runs at 5400RPM, while the higher-capacity Toshiba S300 Pro 10TB steps up to 7200RPM with a 256MB cache for stable write performance when several high-definition streams record at once.

Sizing by system type

• Small 1–4 camera home setup, short retention: a Seagate 1TB CCTV/DVR hard drive covers roughly 1,000 hours of recording on lower resolutions.
• 4–8 camera home or small business system: a 4TB surveillance drive is a common baseline, scaling to 10TB where retention or camera count runs higher.
• Multi-site or compliance-critical retention: pair capacity with RAID redundancy and an offsite backup, since a single failed drive shouldn't mean losing evidence a UK GDPR/ICO CCTV code request might need.

The key takeaway: match drive capacity to actual bitrate × retention days, and always specify a surveillance-rated HDD over a desktop drive for continuous recording.

How Do You Calculate the Right CCTV Hard Drive Size?

Storage capacity comes down to three known inputs: how many cameras you're running, the bitrate each one generates (set by resolution and compression), and how many days you legally or operationally need to keep footage.

The core formula: camera GB-per-day × number of cameras × retention days = total GB required, with spare capacity added on top.

Working out GB-per-day

A single 1080p camera recording continuously on H.265 typically writes somewhere in the region of 8–15GB per day; a 4K camera can run to several times that figure. Actual numbers shift with bitrate settings, scene activity, frame rate and compression efficiency, so treat these as planning estimates rather than fixed specs.

Running the sums

Multiply your per-camera daily figure by the number of cameras, then by the retention period in days — an 8-camera site at 10GB/day needing 30 days' retention needs roughly 2,400GB (2.4TB) before headroom. Always add 20–30% spare capacity, because most DVRs and NVRs either slow down or start overwriting the oldest footage the moment a drive fills completely.

Sizing against real drives

Once you have a target figure, match it to an actual product rather than rounding in your head:

Retention need	Suitable drive
Light use, single camera, short retention	Seagate 1TB SATA Hard Drive for CCTV & DVR
Small multi-camera system	Seagate SkyHawk 4TB CCTV Hard Drive for DVR/NVR at £102.35
Larger sites, long retention	Toshiba S300 Pro 10TB Surveillance HDD at £343.85

Motion-only or event-triggered recording cuts data volume significantly compared with continuous 24/7 capture, which is worth revisiting before you buy a bigger drive than you actually need.

How Many TB Do You Actually Need for CCTV Storage?

Most UK homes and small shops running 4–8 cameras on 30-day retention land somewhere between 2TB and 10TB, with the exact figure driven by resolution, camera count and whether recording is continuous or motion-triggered. Get the sizing wrong and you either overpay for headroom you'll never use or run out of retention days before a claim can be reviewed.

Sizing by setup

• 1–4 cameras, 1080p, motion-triggered, 30-day retention: 1TB is often enough for lighter loads. The Seagate 1TB SATA hard drive for CCTV & DVR is built for 24/7 video recording and supports around 1,000 hours of storage, which suits a handful of motion-activated 1080p cameras rather than continuous multi-camera recording.
• 4–8 cameras, 1080p–4MP, continuous recording, 30 days: 4TB is a sensible working baseline for most small sites. The Seagate SkyHawk 4TB CCTV hard drive (£102.35) or the Toshiba S300 4TB surveillance drive both support multi-camera recording without dropping frames on sequential writes.
• 8+ cameras, 4K, continuous recording, 30+ days: step up to 10TB. The Toshiba S300 Pro 10TB surveillance HDD (£343.85) is engineered to hold stable write performance with multiple high-definition streams recording simultaneously — the workload that fills lower-capacity drives fastest.

Note that some suppliers list the same SkyHawk 4TB drive at differing prices depending on retailer and bundle, so always check the live price on the exact product page before ordering rather than assuming one figure applies everywhere. As a rule of thumb, continuous ("24/7") recording can use several times the storage of motion-triggered recording at the same resolution and retention period, which is usually the single biggest lever when a 2TB drive proves too small.

Why Do CCTV Systems Need a Surveillance-Grade Hard Drive, Not a Desktop HDD?

A desktop hard drive is engineered for short bursts of activity with long idle periods, while a CCTV recorder writes several camera streams to disk continuously, 24 hours a day, for years on end — that mismatch is the leading cause of the recording gaps and "HDD abnormal" errors installers see on DVRs and NVRs. Desktop drives simply weren't designed for that duty cycle, and pushing one into a recorder is asking the mechanics and firmware to do a job they weren't built for.

Firmware matters as much as the platter. Surveillance drives such as the Seagate SkyHawk are tuned around sustained sequential writes for multi-camera streams rather than the mixed, stop-start read/write pattern of a desktop PC, according to the Seagate surveillance storage guide. That firmware difference is why a "cctv hard disk" and a standard PC hard disk for cctv can look identical on the spec sheet yet behave very differently after months of continuous recording.

Duty-cycle rating is the other half of the story. Desktop drives are generally rated for lighter, intermittent workloads, whereas drives sold as cctv hard drives — like the Seagate SkyHawk 4TB CCTV Hard Drive for DVR/NVR at £102.35 — are built around the always-on nature of DVR and NVR recording. The Toshiba S300 Pro 10TB Surveillance HDD is described by its manufacturer as engineered to maintain stable write performance in sequential video recording environments with multiple high-definition cameras recording simultaneously.

For any cctv with hard drive setup running around the clock, treat "surveillance-rated" as the baseline spec, not an upsell — it's the difference between years of unattended reliability and drives that fail quietly under sustained load.

What's the Difference Between the Seagate SkyHawk and Toshiba S300 Drives?

Both are surveillance-class 3.5-inch SATA drives built for continuous recording, but they differ in spindle speed, cache and capacity range on offer. The Seagate SkyHawk 4TB CCTV Hard Drive for DVR/NVR runs at 5900 RPM with SATA III connectivity and ImagePerfect firmware tuned for multi-camera write loads, and it's priced at £102.35. The Toshiba side splits into two tiers worth knowing apart: the Toshiba S300 4TB SATA Surveillance Drive spins at 5400 RPM, while the Toshiba S300 Pro 10TB Surveillance HDD steps up to 7200 RPM with a 256MB cache and costs £343.85.

The practical takeaway: match spindle speed and capacity to camera count, not brand loyalty.

Where each fits

• SkyHawk 4TB – a solid mid-tier choice for smaller multi-camera setups where 5900 RPM keeps noise and heat down while still handling sequential surveillance writes.
• S300 4TB (5400 RPM) – the quieter, cooler-running option for lower channel counts or budget-conscious installs.
• S300 Pro 10TB (7200 RPM, 256MB cache) – built for busier systems needing stable throughput across many simultaneous high-definition streams and far longer retention before the drive fills.

Neither range is a rebadged desktop drive — both are firmware- and vibration-tuned for 24/7 recording rather than intermittent PC use. For a like-for-like decision, weigh RPM against your channel count and required retention days: higher RPM and cache generally suit denser multi-camera DVR/NVR setups, while lower RPM options suit lighter-duty CCTV hard drive installations where quiet running matters more than peak throughput.

Recommended kit

For the setup above, this is the kit we'd fit from our own range:

• Seagate SkyHawk 4TB CCTV Hard Drive for DVR/NVR — Seagate SkyHawk 4TB surveillance hard drive optimised for 24/7 DVR and NVR recording. SATA III, ImagePerfect firmware, multi-camera support. £102.35.
• Toshiba S300 Pro 10TB Surveillance HDD — Toshiba S300 Pro 10TB surveillance hard drive for DVR/NVR systems. 3.5" SATA III, 7200 RPM, 256MB cache. Optimised for 24/7 continuous recording. £343.85.
• Toshiba S300 4TB SATA Surveillance Drive — Toshiba S300 4TB surveillance hard drive for DVR/NVR systems. 3.5" SATA III, 5400 RPM, optimised for 24/7 CCTV recording. In stock.
• Seagate 1TB SATA Hard Drive for CCTV & DVR — Seagate 1TB Pipeline HD SATA hard drive for 24/7 video recording. 5900 RPM, ultra-quiet, supports 1,000 hours storage.