The disk is the heart of a camera system — without it there's no recording. A bad disk means lost data, dropouts and headaches. This guide explains why not to buy just any disk and how to calculate the right capacity.
SSD vs HDD — what for cameras
HDD (mechanical disk)
- ✅ Large capacity at reasonable cost (2 TB ≈ EUR 60)
- ✅ Specialised "Surveillance" lines for 24/7 operation
- ✅ Long lifetime (5+ years with correct use)
- ❌ Slower access
- ❌ Sensitive to shock
- ❌ Noisy, has moving parts
SSD (flash disk)
- ✅ Fast, silent, shock-resistant
- ✅ Low power and heat
- ❌ Higher cost per GB (2× to 4× pricier than HDD)
- ❌ Limited write endurance — cameras write continuously, SSD wears out faster
- ❌ Most NVRs are not optimised for SSD
Recommendation: For 99% of installations choose HDD from a specialised Surveillance line. Use SSD only where shock resistance is required (vehicle, boat).
Which HDD lines to choose
A regular "office" disk (WD Blue, Seagate Barracuda) is NOT built for 24/7 writing. It might last 6 months, then fail. Choose a Surveillance line:
- Western Digital Purple — designed specifically for camera systems. 180 TB/year workload, optimised for continuous writing from multiple cameras.
- Seagate SkyHawk — Seagate's equivalent line. Capacities 1 TB to 20 TB.
- Toshiba S300 Surveillance — alternative, good price/performance.
All our hard drives for camera systems come from Surveillance lines.
Calculating required capacity
Disk size depends on:
- Number of cameras
- Resolution (2 MP, 4 MP, 8 MP)
- Bitrate (how many Mb/s the camera generates)
- Retention period (7, 14, 30 days)
- Recording type — continuous vs motion
Approximate bitrate by resolution
- 2 MP (1080p) — 2–4 Mb/s
- 4 MP (4K lite) — 4–6 Mb/s
- 5 MP — 5–8 Mb/s
- 8 MP (4K) — 8–12 Mb/s
Formula
Capacity (GB) = cameras × bitrate (Mb/s) × 10,800 × retention days ÷ 8,192
Explanation: 10,800 = seconds in 3 hours (most disks average 3 h of continuous recording per day with motion detection), 8,192 = Mb → GB conversion.
Note: For purely continuous (24/7) recording, use 86,400 instead of 10,800.
Practical examples
- 4× 2 MP cameras, motion detection, 14 days: 4 × 3 × 10,800 × 14 ÷ 8,192 ≈ 222 GB → 1 TB is plenty
- 8× 4 MP cameras, motion detection, 14 days: 8 × 5 × 10,800 × 14 ÷ 8,192 ≈ 740 GB → 2 TB
- 16× 4K cameras, continuous 24/7, 30 days: 16 × 10 × 86,400 × 30 ÷ 8,192 ≈ 50,625 GB (50 TB) → RAID array or 4× 16 TB
I recommend adding a 30–50% buffer for unexpected traffic.
One big disk or several smaller ones?
- One big (8–16 TB) — simpler, cheaper per TB. If it fails, you lose everything.
- RAID 1 (mirror, 2 disks) — if one fails, the other holds. Effective capacity is half.
- RAID 5/6 (3+ disks) — only for big NVRs. With one disk failing everything keeps working.
PATRONUM PRNVR series support 1–8 disks. For critical applications consider RAID 1 from two disks — small price increase, big data security.
Formatting and installation
On first connection the NVR automatically formats the disk (must be empty or in a free slot). Don't take the disk out of a PC — the NVR uses its own filesystem.
For disk installation see Installing the hard drive into the recorder.
Summary
- For cameras use Surveillance HDDs (WD Purple, Seagate SkyHawk), not a regular disk.
- Size by formula: cameras × bitrate × 10,800 × days ÷ 8,192.
- Add 30–50% buffer.
- For critical applications consider RAID 1.