By the SightShield team · · 3 min read
Why CCTV needs a surveillance disk
A CCTV recorder writes video 24 hours a day, every day, often from many cameras at once. Desktop hard disks are designed for short bursts of activity and fail early under that load. Surveillance disks are built and tuned for continuous writing, with firmware that reduces dropped frames when many streams arrive together. A failed disk is the most common reason CCTV footage is missing — so this is not the place to save money.
The two families
| Seagate SkyHawk | WD Purple | SkyHawk AI | WD Purple Pro | |
|---|---|---|---|---|
| Workload rating | Up to 180 TB/year | 180 TB/year (some larger models higher) | 550 TB/year | 550 TB/year |
| Cameras supported | Up to 64 HD streams | Up to 64 cameras | Built for AI NVRs | Built for AI NVRs |
| Frame-loss firmware | ImagePerfect | AllFrame | ImagePerfect AI | AllFrame AI |
| Warranty | Check local terms | 3 years | 5 years | 5 years |
| Typical use | DVRs and NVRs in homes and businesses | DVRs and NVRs in homes and businesses | Large or AI-heavy systems | Large or AI-heavy systems |
What the workload rating means
Workload is the amount of data written to and read from the disk in a year. A small home system writes well under the standard 180 TB/year rating. Large NVRs with dozens of 4MP or 8MP cameras, continuous recording and frequent playback can approach it — which is when the Pro/AI versions make sense. Running a disk beyond its rated workload shortens its expected life.
Extras
- Seagate offers Rescue data-recovery services on many SkyHawk models (availability varies by country).
- Both brands provide health-monitoring tools, and most recorders show disk status.
- Both offer large capacities; most recorders accept one or two disks, larger NVRs more.
Signs a CCTV hard disk is failing
- The recorder shows “HDD error”, “abnormal” or “no disk”.
- Recordings have gaps or the playback calendar shows missing days.
- The recorder reboots by itself or beeps.
- Fewer days of recording than expected for the same settings.
- Clicking or grinding sounds from the recorder.
Buying genuine disks
Refurbished or grey-market disks are sometimes sold as new. Buy from authorised channels, check the serial number on the manufacturer’s warranty page after purchase, and keep the invoice. A disk sold without valid warranty is a warning sign.
Genuine vs Grey-Market CCTV Cameras →Which one should you choose?
For homes, shops and offices, either standard family works well — choose on availability, warranty support and price. For large NVRs, AI-heavy recording or sites that keep 60–90 days, step up to SkyHawk AI or Purple Pro. Whatever you choose, buy genuine stock with an invoice and replace disks when the recorder warns of health problems.
CCTV AMC with disk health checks →Example: sizing disks for a 16-camera office
An office with sixteen 4MP cameras wanted 30 days of continuous recording. Using the rule of thumb of about 20 GB per 4MP camera per day, that is roughly 16 × 20 × 30 = 9,600 GB, so about 10 TB. The NVR has two bays, so two surveillance disks of 6 TB each give about 12 TB — enough headroom for busy days and night-time bitrate increases. Either SkyHawk or Purple fits; the choice came down to price and local stock on the day. The serial numbers were checked on the maker’s warranty page before installation.
Genuine vs grey-market CCTV →Quick answers
Can I use a normal desktop hard disk in a DVR?+
It may work at first, but desktop disks are not designed for 24×7 recording and tend to fail early. Use a surveillance-grade disk.
How long does a CCTV hard disk last?+
Surveillance disks commonly last several years in continuous use. Heat, power cuts and heavy workloads shorten life.
Is SkyHawk better than WD Purple?+
They are closely matched in their standard versions. Choose based on availability, warranty support and your recorder’s compatibility list.
How many days will a 4TB disk record?+
It depends on the number of cameras, resolution, compression and motion. Use our hard disk calculator for an estimate.
Should I replace the disk before it fails?+
Replacing disks proactively after several years of 24/7 use, or when health checks show warnings, avoids losing recordings.
How long do surveillance hard disks last?+
Often three to five years of continuous recording, depending on heat and workload. Replace them proactively on critical sites.
Can I use a desktop disk in my NVR?+
It may work for a while, but desktop disks are not designed for 24-hour writing and fail sooner. Use surveillance-rated disks.