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How to Select the Right NVR

As IP video increases, network storage has become a hot topic. Sunell discusses key aspects of NVRs and how to select them.

What is an NVR?
Unlike DVRs, network cameras usually support only SD card recording. However, SD card capacity cannot meet customer demands for long-term video storage, serving as emergency backup for recording about a day's images. IP surveillance systems therefore need network storage for long-term recording archival requirements. There are currently three choices for network storage:

NAS (IP SAN): Most NAS or IP SAN solutions use commercial storage equipment, usually from IT storage manufacturers. They are deployed for many IP video surveillance systems, but tend to be pricey. In the long-term, NAS or IP SAN will not be the dominant storage medium for IP video surveillance system.

Hybrid DVR: To address the higher prices of NAS or IP SAN storage, some DVR manufacturers have added network camera integration to their DVRs, enabling IP video storage. However, the DVR's main control unit inside can only handle processing for a handful of network cameras. Therefore, hybrid DVRs are limited to smaller projects using both analog and network cameras.

NVR: NVRs are currently hot, but features and functionality are far from standardized. Specifications differ greatly by vendor. Sunell discusses some of its criteria for providing an effective NVR below.

The considerations in the article have influenced Sunell's NVR design. It defines NVRs asHigh resolution is a key advantage of network cameras. Ranging from 1-megapixel, 2-megapixel or higher-count models, the images require added bit rates and thus more storage. For example, a 2-megapixel camera's bit rate is about 6 megabits per second (Mbps), so storing footage for a month would require nearly 2 TB of hard disk space, or the current maximum capacity of a single hard disk drive (HDD). That means a 1- or 2-megapixel camera needs at least one HDD for storage. A NVR with an eight-bay HDD storage only can support eight megapixel cameras.

Therefore IP surveillance has great demand for storage. The NVR's price cannot be too high. NVR costs will be a key factor for continued adoption of network cameras in the market.

NAS and IP SAN storage are based on commercial hot-swappable hard drive designs similar to drawers, while DVR drives are usually built as fixed internal drives. As network storage emphasizes scalability, it remains to be seen if NVRs will maintain a single-unit design like DVRs or adopt IT's approach with hot-swappable arrays.

High Reliability
NAS and IP SAN solutions usually support RAID technology for high reliability. The concept of RAID is redundancy, as damage to a single byte of data is unacceptable for some organizations, making enterprise data storage valuable.

However, IP video surveillance applications are different, as a small amount of data loss will not dramatically reduce monitoring effectiveness. RAID also requires more space for the HDDs. Thus RAID technology is not applicable for most surveillance application. NVR device-level redundancy is a better way of ensuring reliability. Security professionals can deploy multiple NVRs in a group, so if a device fails, another one can automatically take over the failed NVR's tasks.

Embedded Software
What kind of embedded software in a NVR decides what role the NVR can play in the IP surveillance system. Some NVRs only have simple software inside, which role is somewhat a secondary storage device as NAS/ IPSAN. Adopting this kind of NVRs, several PCs are still needed to deploy video management software (VMS). So the whole cost of the IP surveillance system will be high and complex. The better solution is NVR embedded a complete VMS. Then the IP surveillance system can be made up of only network cameras and NVRs. However, designing a cost-effective NVR with complete VMS functions is a big challenge for NVR manufacturers.

Decoding Capability
NVRs are not only storage devices. They must also support real-time video monitoring, which requires real-time video decoding capabilities. The number of H.264 profiles the NVR can decode will be a key technical specification. If an NVR can only decode MP-level H.264 video streams, it will soon go out of date. Because future network cameras could support HP-level H.264 encoding, newer cameras will be unable to connect to the NVR.

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