You can estimate how large a hard drive is needed by inputing the information in steps 1 through 7. This is only an estimate since complexity of scenes which can affect the space required will vary but this will provide a good idea of the hard drive space required.
1. Choose Camera Stream: H.264 most common (DVR and NVR)
2. Choose Camera Resolution: QCIF (176x144), CIF (352x288), 1.3 Megapixel (1280x960), 2CIF (704x288), 2 Megapixel (1920x1080), 4CIF (704x480), 3 Megapixel (2048x1536)
3. Video Quality: Highest, Normal, Low (the average frame size will auto adjust)
4. Number of Cameras: Select how many cameras will be recording
5. Frame Rate per Camera: real time is 30 FPS but is not needed, selecting even 7 to 12 FPS is adequate for most situations and saves space.
6. Hours Each Camera Will Record per Day - If recording only on motion, which can significantly save space, you will need to estimate how many hours each camera will record
7. Desired Storage (Number of Days) per Camera - This is the number of days recordings will be saved on the hard drive before the oldest data starts to be overwritten
8. Total Bandwidth Required Per Camera will then be displayed along with Estimated Storage in GB (Gigabytes) or TB (Terabytes)
*Tips for saving hard drive space: * 30 frames per second is real time. At 3 - 5 frames per second recording you will not miss any activity (remember this is per second) * There is no real need to record in real time unless there are regulatory reasons as in case of government facilities or casinos.