A firmware update was recently released for the NVR6XX-4KS2 series devices.
Information, instructions, and download links can be found Here
Troubleshoot/NVR/Need More Recording Space
From Dahua Wiki
Record storage period is not enough
If your storage drive is filling up quickly and you want to maximize on the time you are recording please consider the following:
1. HDD capacity is not enough, so you might need more storage space or The HDD is damaged or the space is fragmented and unusable. Depending on how many cameras, resolution, scene, frame rate, bit rate etc. it is recommended to use a storage calculator to determine the appropriate HDD capacity.
2. You could set the resolution to a lower setting, but the ratio of bit rate to resolution is not always 1:1. Also some cameras process lower resolutions better than other, and the same goes for higher resolutions. Although the ratio can vary from 0.6:1 to 2:1 (bit rate : resolution)
3. Recording a scene that is constantly busy can cause higher storage usage (or recorded bit rate over time). Objects such as plants moving in the wind, vehicle traffic, or public areas are often a cause of higher bit rates. This is directly related to the compression used on the stream since still images are easily reduced by repeating pixels in still areas.
4. The compression method might not be optimally set to the best suited compression. When you ask for a higher amount of compression (lower bit rate) you are inherently going to sacrifice the quality of the image. Most configurations use H.264 compression, if you want the least amount of loss in quality use MJPEG. Some of our cameras support H.264B (higher compression and lower quality than H.264), and H.264H (lower compression and higher quality). Also a new standard on the horizon is H.265, which is mostly used for high resolution applications, and they require both an encoder (i.e. a camera) and a decoder (i.e. a NVR) to be complaint with the H.265 standard.
6. Recording constant image noise will cause higher storage usage. Image noise is caused by vibrations on the camera itself. The cause for this can range from high winds, vibration on the wall (sometimes cause by a mechanical device mounted to the same wall i.e. an air conditioner), or mounting a camera to a moving object (i.e. a tree). There are some remedies to this such a dampening the vibration with an image stabilizing lens and/or a chip set feature embedded into the camera.
7. Instead of constant recording you can set the record schedule to motion detect which will make the video file shorter, however depending on how you set the camera up you might miss fast moving objects.
8. You may set the record to sub stream instead of main stream, this will have the same effect as lowering the resolution. In addition it defeats the purpose of having the higher resolution main stream. You may also disable the sub stream from recording, however this can cause problem with viewing the sub stream while viewing multiple cameras on one screen.
9. The Bit rate can also be set too high. Changing the bit rate from CBR (Constant Bit Rate) to VBR (Variable Bit Rate) can save space on the HDD. CBR prioritizes that specific feed over other cameras and sends a larger amount of data through, so setting all feeds to CBR can be an issue is some cases. Using VBR you can set the quality of detail higher or lower from 1 to 6 (1 being lowest quality) in order to also get a lower bit rate.
10. The frame rate could be too high resulting in bigger files. Frame rate is the rate of capture over a second, and exposure time is how long that individual capture takes in that second. A typical frame rate in the security industry ranges from 7 to 10 frames per second (FPS). However when you need to record fast moving objects quickly you will probably want 10fps or more, and also a well lit area with a faster shutter speed to prevent motion blurring.
11. Lighting scenarios can be a problem when it comes to low light noise being recorded. When in low light or total darkness the sensor sometimes tries to allocate information it cannot see, or an image that is not fully lit. This means the camera has to recognize areas of total darkness as a still image, and then compress it, which can be problematic. If the CCD or CMOS sensor is not designed for low lighting settings (specified by lux rating) and lacks IR then you will have a larger file recording since the picture will be generating a random grainy picture. There are technologies that do help process data better, such as starlight cameras, and cameras with infrared light emitters.
12. Wide Dynamic Range better known as WDR, is a post processed image that scales several exposures into one image. The result of using WDR is a picture with dark and light areas seeming to have even or clear exposure to them. Turning up WDR causes more processing and noise in an image, which in turn will increase the bit rate of the stream. WDR levels are measured in DB, the higher the DB the more displacement of lighting WDR can handle, but also it includes a higher bit rate and lower contrast of the image.
13. Over saturation of a picture, or bumping up the color settings can cause false readings on a color and create image noise, which would increase the bit rate of your stream. Try to keep the colors as true as possible using a camera test chart and a properly calibrated monitor.
14. The field of view also has an influence on the bit stream rate. Field of view is how wide of an area the camera see's from it's point of view. With a fish eye camera you will have a large field of view, and with a 20x optical zoom lens you will have a narrower field of view. Since the bit rate is influenced by movement, inherently a wider field of view will yield more movement captured as intended, causing a higher bit rate.
15. Increasing the sharpness on a camera will also yield more detail, therefore once the details change there will be more movement simulated, causing the bit rate to go up.