Analog CCTV storage

When buying a security DVR system on a strict budget, one of the features you will want to pay special attention to is the amount of storage that comes with your DVR. You’ll want to keep a enough archived history in case you’re out of town or away from your home / business for an extended period of time, but how much storage is enough? Do you want to gamble and keep enough storage for just a handful of days? A week? A month? The longer the time frame, the more storage you’ll need.

Key Factors Affecting the Amount of Storage Space

• # of Days Required
• Quality of Cameras (# of TVL / Megapixels)
• DVR Motion Settings
• DVR Record Rate

For the sake of argument and nice round numbers, we’ll say that a 400 TVL camera takes up 1 MB of memory per minute of recorded footage. By those numbers, a 500GB hard drive would be able to record 512,000 consecutive minutes, or 355.56 days, of completely fictional video footage. Now, let’s say we have a 600 TVL camera that occupies 2.5 MB of memory per minute of recorded footage. That means that the same 500GB hard drive will only be able to record 204,800 consecutive minutes, or 142.22 days, of fake video feeds.

Q: How do I decide how much storage capacity to allow when I'm specifying a digital video recorder?

A: There's no simple answer – every installation must be assessed individually. Key factors affecting storage are picture quality, frame rate, compression method and the length of time for which images are required.

Q: What are the picture quality options?

A: The lowest resolution now normally adopted is CIF (352X288). CIF is generally the rule of thumb when calculating storage capacity, but higher resolutions, such as 2CIF (704X288), 4CIF (704X576) and D1 (720x576), are now often specified. As a guide, CIF images recorded using MPEG4 compression are around 10Kb, 2CIF images around 20Kb and 4CIF around 40Kb. Megapixel cameras usually produce images between 80 and 200Kb each. A balance must be struck between resolution, archive time and budget.

Q: What about frame rates?

A: Always allocate frame rates appropriate to the application. Live motion is 25 full frames-per-second (fps) but each image can be 40Kb or more (4CIF). This means about 1Mb of storage per second of data from each camera – about 3.6Gb per hour. Using 12.5 fps halves storage requirements and still permits lip-sync audio. Where lip sync isn't needed, 4 fps is often acceptable, with corresponding savings in storage.

Q: How do compression methods affect the amount of storage?

A: Significantly! The challenge is to reproduce high quality, high-resolution video using the smallest amount of drive space, but remember that there are no free lunches! If a DVR claims much smaller file sizes than comparable machines with the same compression method, beware – reduced file sizes usually mean reduced quality.

Q: How long should recordings be kept?

A: This depends on the application, but don't automatically adopt the "31-day standard", a hangover from VHS tape. Digital recording is much more flexible. Discuss the options and costs with your client. In general, look at periods where video data cannot be recovered. If this happens to be 20 days, then 20 to 22 days of archive are appropriate.

Q: Is there no easier solution?

A: When in doubt, seek the advice of several professional suppliers to ensure a balanced view. Also, remember that storage is now much less expensive, so over-specifying a little won't significantly affect project costs.

If your DVR has 4SATA/6SATA/8SATA etc then your DVR can take 30days/60Days/90Days/120Days etc. You can used 1TB/2TB/4TB SATA hard Disk for storage. Capture 16-channel DVR Model: DTR4816HD has 8Port SATA.

If we use an ATX Footprint two 9U Rack Enclosures. Each one is Heavy, very nearly 100 Lbs with NOTHING in it. Each Enclosure has 50 Hot Swap Bays for Hard Drives and Two Hard Mount Locations. Today we can put 4.0 Terabyte Hard Drives (SATA-600) in there...up to 100 of them in each of the boxes These drives are SATA Drives with 128 Mb of cache on each one. Additionally, we can add two more hard drives in a hard mount. That gives us up to 400 TB of Storage. As hard drive sizes continue to grow, our storage capability increases. What was literally out of reach for many organizations just a year or so ago, is easy to attain today. You may use 8 Drive, 12 Drive, 16 Drive & 24 Drive Enclosures available.

Extra Note: By Western Digital on Date: 03/12/2014

One major component of every surveillance system is, of course, the cameras. Buyers should opt for kits that offer nothing less than a High Definition (HD) camera that can capture images at a resolution of 1,280 x 720 pixels or even a Full High Definition (FHD) camera that can capture images at 1,920 x 1,080 pixels. High resolution image capture is important as it becomes easier to spot what users are looking for when reviewing the surveillance footage – the last thing users want is for a perpetrator's face (as an example) to be a mess of indistinguishable pixels. And, whether HD or FHD, the cameras should also be able to capture images at a rate of no less than 30 frames per second (FPS). This, again, will help when it comes to reviewing crucial footage.

An equally key component of surveillance systems is the storage being used – in fact this component is what can really make or break the effectiveness of the entire system. If a system is being purchased without storage, the buyer should avoid the temptation to go out and purchase the cheapest hard drive he can find. In most cases this will be some sort of desktop drive that is not designed for 24/7 use, won't be able to capture HD or FHD video from multiple cameras without dropping frames and isn't designed to consume less power and thus generate less heat. This last point is a major concern in terms of reliability, as excessive heat can drastically reduce the life of a hard drive and can also adversely affect read and write operations when the drive is being used in the surveillance system.

A buyer should, ideally, look for hard drives that offer surveillance-relevant optimizations such as AllFrame technology, which not only improves playback performance but works with ATA streaming to reduce errors and frame loss. The drives should also be designed for 24/7 usage and offer features such as IntelliPower, which enables a drive to consume less power and thus generate less heat. This is ideal when a drive is going to be installed in a passively cooled storage enclosure, whether on its own or in-conjunction with several other hard drives.

Considering the high importance of storage in surveillance systems, vendors such as WD have introduced dedicated table-top surveillance drives that boast the aforementioned technology optimizations. The recently introduced WD Purpledrive family has been compatibility tested with hundreds of surveillance systems and offer up to 4TB of capacity on a single drive. Purple drives are uniquely designed for mainstream surveillance systems and offer the perfect blend of performance, reliability and cost - the drives are recommended for use in systems with between 1-to-8 drive bays and where between 1 to as many as 32 HD cameras are used.

Besides selecting the right type of drive, one also has to consider the amount of storage that is needed. Just how much storage is needed varies depending on the specifications of the cameras and then length of time users intend to keep your video surveillance data. The amount of time businesses maintain surveillance data varies drastically but the norm is gradually shifting from as little as 7 days to 30 days. (Certain organizations are legally required to retain data for even longer periods of time.) A general rule of thumb is the longer you are able to retain data, the better it is.

Since the video surveillance enter into megapixel IP era, the required storage capacity significantly increased, which directly increased the demands for hard disc drives.  Western Digital chose to cooperate with Hikvision to launched Purple series HDDs which are dedicated for video surveillance application. Seagate also launched ST4000VX000, which is a surveillance HDD addresses the increasing need for high-resolution cameras and camera counts, and ensures cost-effective performance and durability in always-on surveillance systems. when decide to use HDD, the first thing you want to consider is capacity. You may need to estimate the storage capacity for required video recording. Typically users opt to save costs by simply matching current capacity needs to your video surveillance demands. However, this may actually cost you more and create more upgrade issues in the long run. To choose the HDD capacity, you may take your future needs into consideration. The 4K video resolution is for times higher than your full HD 1080p resolution, which in turn, resulting in requires more than four times the amount of storage space as 1080p. Now, 500GB HDD will disappear from market, the maximum HDD storage capacity can reach up to 6TB, which can provide enough storage capacity for 64 cameras.

Do not use regular desktop computer HDDs for video surveillance. Since the working environment and condition is different, video surveillance requires a HDD that's not susceptible to the issues including heat-related failure or vibration from other drives, which can result in loss of video frames, data loss. What's the difference between regular computer HDD and surveillance dedicated HDD? Compared with computer HDD, surveillance dedicated HDD are designed for 90% write time and only 10% read time. The surveillance-specific drives are also engineered to reliably perform in multi-drive systems with RAID support. Optimized performance and reliability can minimize the effect of vibration from other drives with RV sensors, which mean fewer points for potential failure.

Here we have provided Storage size of Cameras in GB per Day according to their Formats H.264 Compression.

Resolution	Storage Per Day in GB
1 MP	25-30 GB Aprox
2 MP	35-40 GB Aprox
3 MP	60-65 GB Aprox