Find out exactly how many hard drives your NVR needs. Enter your cameras and retention period — get a drive count, total capacity, and RAID recommendation.
Most NVR sizing guides give you rough estimates based on 'average' cameras. This estimator calculates storage from the actual bitrate your specific cameras produce, taking into account resolution, codec, scene complexity, motion percentage, and recording schedule. It then recommends surveillance-grade drives (WD Purple, Seagate SkyHawk) in the right capacity tier, with RAID configuration matched to your deployment size. Works with all major NVR brands: Hikvision DS-7600/DS-9600 series, Dahua NVR4000/NVR6000, Uniview, Milesight, and any generic ONVIF NVR.
A fully loaded 16-channel NVR with 4MP H.265 cameras at 20 FPS (30-day retention) typically needs 8–12 TB of usable storage, or 2–3 drives of 4–6TB in RAID 5. If you're running 8MP cameras or H.264 instead of H.265, expect 2–3× more storage for the same retention period.
Use surveillance-grade drives rated for 24/7 operation: Seagate SkyHawk (1–16TB), WD Purple (1–18TB), or WD Purple Pro (8–18TB) for high-load systems. Standard desktop drives are not designed for the constant write cycles of NVR recording and fail significantly faster in this application.
For JBOD (no RAID) setups, yes — the NVR treats each drive independently. For RAID configurations, use identical drives. Mixing sizes in RAID forces all drives to operate at the size of the smallest drive, wasting capacity on larger ones. Always plan your RAID with identical drive models.
A single 4TB drive holds approximately 20–30 days of footage from one 4MP H.265 camera recording continuously. For 8 cameras, divide that by 8 — so about 2–4 days. For multi-camera systems, you typically need multiple drives and RAID to meet retention requirements. Use this estimator to get the exact figure for your setup.
Yes. Every camera writes simultaneously, so your total write throughput is the sum of all camera bitrates. At 16 cameras × 3 Mbps = 48 Mbps sustained write. A single SATA drive handles ~150 MB/s, so throughput is rarely the bottleneck for under 50 cameras. Above 100+ cameras at high bitrates, you need multiple drives or an NVMe cache tier to avoid dropped frames.
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