Top 5 Problems in Video Surveillance Storage

By John Honovich, Published Dec 20, 2008, 07:00pm EST

Storage is one of the most confusing and debated aspects of video surveillance solutions. Continuously rising expectations for TV or HD quality combined with falling storage prices only makes the issue more challenging.

Here are the top 5 storage issues we are facing:
  • Demanding TV Quality Resolution
  • Demanding TV Frame Rates
  • Requiring Continuous Recording
  • Assuming Storage Cost is free
  • Solving Camera Problems with Storage

Demanding TV Quality Resolution

Security is not entertainment.  While there are applications that can benefit from TV or HD quality resolution, designers and users need to be very careful about automatically requiring TV or HD quality resolution.

As a business tool, surveillance video should be good enough to solve the incidents that are captured and no better. Very frequently, VHS level quality (e.g., CIF) is good enough to accomplish this. As we will examine, differences in resolution have massive impacts on storage costs.

Demanding TV Frame Rates

Surveillance video almost never requires the same frame rates as TV or movies. While 25-30 fps of entertainment video is important for entertainment, almost all security problems can be solved with video of no more than 5 - 10 fps.

How smooth the surveillance video playbacks is rarely an issue as it only affects investigations if an incident happens extremely quickly (e.g., less than 1/20th of second). This only is relevant in niche cases like dealing cards in casinos and is generally not a concern.

And, just like resolution, frame rate settings have significant effects on storage costs.

Requiring Continuous Recording

In entertainment video, long gaps in between scenes would be frustrating and not feasible. However in surveillance video, no motion almost always means no security concern. As such gaps in video is generally not a security concern.

Using motion based recording can reduce storage costs by 80% and is one of the most successful uses of video analytics.

The risk and problem of using motion based recording is (1) missing an incident and (2) acceptability in court.  Missing an incident is very rare and should almost never happen if the detection threshold is set low (see the motion detection report for details). Acceptability in court is also rarely an issue as (1) often simply placing the suspect at the location of the crime is sufficient. Nonetheless, I accept that some organizations do not want to risk courts throwing out evidence. For them, they can use a combination of continuous recording at a low frame rate and motion based recording to increase the frame rate when motion is detected.

Assuming Storage Cost is Free

Storage costs can be very high depending on your settings.

The table below demonstrates that storage settings dramatically impact storage costs. Selection of resolution, frame rate and recording mode can change your storage costs by 20x.

This is for a single cameraso you can easy see how expensive storage can get for systems with dozens or hundreds of cameras.  
  • For CIF resolution, 5fps, Motion based recording using H.264 codec for 90 days, total storage required is approximately 100 GB and cost $150 USD.
  • For 4CIF resolution, 30fps, Continuous recording using H.264 coed for 90 days, total storage required is approximately 4200 GB and cost $4,000 USD.

Pricing is in USD and represents an average approximation of today's storage costs. 

Storage costs are often ignored because (1) storage prices continuously fall and (2) too much focus is placed on the cost of individual hard drives.

While storage costs continuously fall, they are certainly still a major factor in overall surveillance costs. Moreover, falling prices does nothing for people buying today (except to encourage them to delay purchasing).

While hard drive prices look cheap, the cost of storage is significantly more than individual drive prices. For instance, today, a 1TB hard drive is about $100 USD. However, the total cost of 1TB of storage is closer to $750 - $1500. You cannot simply buy dozens of hard drives by themselves. You need management systems, enclosures and hardware to connect all of the drives (e.g., NAS and SANs). While these are continuing to decline in price, the price is not negligible, especially for surveillance video which can easily demand many TBs per camera.

UPDATE: For small systems when you are using internal storage on a PC/server, the total cost is often simply the price of the additional hard drives. In such cases, you can effectively see the price per TB under $200 USD.  

However, most deployments fall under 1 of the following 2 scenarios: 

  1. You use a proprietary DVR where the DVR vendor is charging you a fortune for storage (see the report on software only for details on why this happens).
  2. You have dozens of cameras and high quality demads requiring specialized storage appliances for the tens of TBs of storage you need.
In either of these two common cases, storage pricing is generally $750 - $1500 USD (or more if it's a DVR vendor).

Solving Camera Problems with Storage

Finally, just because you record at TV quality levels, does not mean your image quality will be good. Some of the most common problems in video surveillance systems is using the wrong type of camera (for the scene) or mispositioing the camera. High quality surveillance video is first and foremost a matter of camera layout and selection. With bad positioning or the wrong camera, your image quality will likely still be bad even if you spend thousands of dollars for higher resolution and frame rate storage.

Conclusion

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Asking hard questions about video surveillance storage is important for cost-effective solutions. I don't expect these problems to be resolved any time soon and I expect the disagreements will continue. Hopefully, this converation will help shed light on key issues involved.

Update: Geoff Moore, in a response to this report, examines a number of real world video surveillance storage cases [link no longer available], including specific recommendations on the best way to optimize. We then discuss the best ways to reduce storage costs over time.

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