How Much Storage Do You Need for 4 CCTV 1080p Cameras for 30 Days?

Understanding the Storage Math for 1080p Surveillance

Setting up a security system is more than just mounting cameras; it is about ensuring that when something happens, the footage is actually there. The biggest variable in security planning is the storage capacity. When we talk about 1080p resolution, we are dealing with a significant amount of data that is being streamed constantly. Unlike a movie you download once, a surveillance system is a continuous stream of data that never stops.

To calculate your needs, you have to look at three main factors: resolution, frame rate, and compression. A 1080p camera (also known as Full HD) produces much more data than a 720p camera. If you are running four cameras at once, those data streams are being aggregated onto a single hard drive. If your bitrate is set too high, you will run out of space in a few days; if it is too low, your footage will look pixelated and grainy, making it useless for identification.

Most modern systems use H.264 or the more efficient H.265 compression. H.265 is a game-changer for storage because it can significantly reduce the file size without sacrificing much visual quality. This efficiency is what makes a 30-day storage goal achievable without needing massive, expensive enterprise arrays. For more on this, see our guide on WD Purple Pro vs Seagate SkyHawk: Which Surveillance Drive Wins?.

Why You Must Use Surveillance-Grade Hard Drives

It is a common mistake to take an old desktop hard drive from a spare PC and plug it into a Network Video Recorder (NVR). While it might work for a week, it is a recipe for disaster. Standard desktop drives are designed for 'bursty' workloads—reading a file, saving a document, or loading a webpage. They are not designed to write data 24 hours a day, 7 days a week, without pause.

Surveillance-specific drives, such as the Western Digital Purple series or the Seagate SkyHawk series, are engineered differently. They feature firmware optimized for continuous write workloads. In a standard drive, if the system encounters a minor error, it might stop to try and correct it, which can cause the video stream to drop frames. Surveillance drives are designed to prioritize the write stream, ensuring that the recording stays continuous even if a minor error occurs.

Furthermore, these drives are built to handle the heat and vibration of a multi-drive NVR environment. In a system with several cameras and multiple disks, the constant mechanical vibration can cause errors in standard drives. Surveillance drives use specialized sensors and mechanical designs to mitigate this, providing the longevity you need for a system meant to protect your property. For more on this, see our guide on Optimizing WD Purple Surveillance Drive Workload for CCTV.

Comparing the Heavy Hitters: WD Purple vs. Seagate SkyHawk

When you enter the market for surveillance storage, you will inevitably find yourself choosing between Western Digital and Seagate. Both brands offer world-class reliability, but they have slight nuances in their product tiers. Western Digital offers the standard Purple line for general surveillance and the Purple Pro line for high-bandwidth, high-camera-count environments.

Seagate's SkyHawk line is similarly tiered, with the SkyHawk AI designed for systems that utilize deep learning and advanced analytics. If you are just running four 1080p cameras, either brand will serve you excellently. However, if you plan to scale up to 32 or 64 cameras in the future, looking at the 'Pro' or 'AI' versions of these drives is a wise investment. These higher-end models are designed for much higher workloads and can handle the massive data throughput required by high-resolution AI processing.

Calculating Your Specific Capacity Needs

To give you a concrete idea of what to buy, let's look at a typical scenario. A single 1080p camera recording at 15 frames per second (FPS) with H.264 compression typically uses about 1.5 to 2 Mbps (Megabits per second). For four cameras, that is roughly 6 to 8 Mbps of constant data being written to the disk.

Over a 24-hour period, four cameras at this rate will consume approximately 250GB to 350GB. To reach a 30-day goal, you would need roughly 7.5TB to 10.5TB of usable space. If you use the more efficient H.265 compression, you can often cut that requirement nearly in half, making a 4TB or 6TB drive more than sufficient for a 4-camera 1080p setup. Always remember that hard drive manufacturers define '1TB' differently than your computer does, so it is always better to over-provision your storage capacity slightly.

Maximizing Your Storage Efficiency

Beyond just buying a bigger drive, there are software settings you can tweak to get more days of storage out of the same hardware. The first is 'Motion Detection' recording. Instead of recording 24/7, many NVRs allow you to record only when movement is detected. This can extend your 30-day window to several months on the same drive, though it does mean you might miss the 'setup' moments before a crime occurs.

Another factor is the Frame Rate (FPS). For many security applications, 15 FPS is perfectly adequate. You don't need 60 FPS (which is used for gaming) to see a person walking through a driveway. By dropping from 30 FPS to 15 FPS, you effectively double your storage capacity without any significant loss in the ability to identify subjects. Combining these settings with H.265 compression is the professional way to manage a surveillance budget.

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