A recorder has to keep up with three numbers: how many cameras it records, how much video arrives every second, and how long that video has to be kept. Get those right, add sensible headroom, and the rest follows.
1. Channels
Count every camera you will record, then add room for growth. A 16-channel recorder for 14 cameras leaves very little space for change. Remember that multi-sensor cameras can use one channel per sensor, depending on how they stream.
2. Incoming bandwidth
Add up the recording bitrate of all cameras. Bitrate depends on resolution, frame rate, compression, scene activity and night-time noise. Compare the total with the recorder's maximum recording throughput, and leave at least 20 to 30 percent spare so that playback and remote viewing do not compete with recording.
3. Storage
The basic formula:
Storage (TB) = bitrate (Mbps) × 0.00045 × hours recorded per day × days kept
The factor 0.00045 converts one megabit per second into terabytes per hour (1 Mbps × 3600 s = 3600 megabits = 450 MB = 0.00045 TB). Do this for each camera, add the results, then add a margin of 10 to 20 percent.
Worked example
| Item | Value |
|---|---|
| Cameras | 12 cameras at about 4 Mbps each (H.265, 4MP, 20 fps) |
| Total bitrate | 48 Mbps |
| Recording | 24 hours a day, continuous |
| Retention | 30 days |
| Storage | 48 × 0.00045 × 24 = about 0.52 TB per day, × 30 days ≈ 15.6 TB |
| With 15 percent margin | about 18 TB of usable space |
Motion or event-based recording can cut this considerably, but plan for busy days, not quiet ones.
4. RAID and redundancy
RAID protects recordings when a drive fails. RAID 1 mirrors two drives. RAID 5 tolerates one failed drive across a set and RAID 6 tolerates two. Remember that RAID uses some raw capacity: usable space is less than the sum of the drives. For sites where losing footage is unacceptable, look at hot-swap bays and health monitoring that alerts you to failing disks.
5. PoE ports and network
Recorders with built-in PoE ports power and connect cameras directly, which keeps small systems simple. For larger systems, use a separate PoE switch and check that the recorder's network interface can carry the total camera bandwidth.
6. Viewing and management
Decide how footage will be watched: a local monitor on the recorder, client workstations, a video wall or mobile devices. Several recorders or sites are easier to run with a central management system.
Send us your camera list and retention requirement and we will check the sizing for you.