How to build a highly available storage solution for network video recording applications.
NVR (network video recording) systems are now widely used in surveillance and security applications, such as building and factory security or rolling stock video surveillance. Because NVRs need to store digital video files, they tend to come with substantial data storage requirements. Mass storage devices such as USB flash drives, SD memory cards, or hard disks can be used to provide the necessary storage capacity.
To get an idea of the requirements of NVR systems, let us look at a common surveillance application, an IP-based train surveillance system. The system uses cameras located throughout the train to record video, has a network of Ethernet switches and uses computers to operate the cameras and store video data. Video servers may also be used if there are analogue cameras in the system. A display is available in the driver’s cabin for real-time video monitoring or video playback of specific files stored on the computers.
Data storage is a key limitation of this type of NVR system, because the entire surveillance system generates a large amount of video data that must be saved for potential review later. In addition, often the train must operate independently, because it is a fast-moving application platform that may not have a secure link with the ground-based network. This means that the NVR storage should be as self-sufficient as possible, and not rely too much on constant off-site storage backups. However, mobility of rolling stock applications poses a separate challenge for the NVR data storage: this is an environment with high vibration and shock, which is a very problematic environment for fragile hard drives to operate in.
Challenges in NVR storage systems
Storage capacity
Delivering sufficient storage capacity is a major challenge in deploying today’s NVR systems. NVR systems that continuously record video require significant storage capacity, and a higher video resolution requires more hard disk capacity. In addition, hard disks need to be replaced, especially if the system is required to maintain a long-term video record. A long-term video surveillance database can be a valuable resource, but to keep this kind of record, hard drives that reach their storage limit will need to be pulled and archived and then replaced with new ones. This can be a time-consuming procedure that substantially increases system maintenance overhead and costs.
Vibration and shock
Vibration and shock is a constant challenge for NVR systems, particularly those deployed on moving vehicles such as trains or buses. Commercial-grade storage media, such as hard disks, cannot withstand the movement and shock that is commonplace on moving vehicles. Vibration and shock can lead to system instability and reduce the lifecycle of the equipment. The most common approach to address this challenge is to use industrial-grade hard disks or solid state drives (SSDs), both of which are extremely expensive compared to commercial hard disks. The price of SSDs also affects how much storage capacity system operators can afford, compounding data capacity limitations in a system that is probably already starved for more data storage.
Maintenance
Maintenance is another ongoing challenge for NVR systems and is related to the two challenges listed above. Storage devices that must be repeatedly replaced impose substantial maintenance costs. In addition, the system must be shut down during the hard drive replacement process. However, insufficient storage, or constant vibration and shock damage, can lead to unsustainable replacement cycles.
Readers wanting to find out how to overcome these challenges using new technology can view the Moxa white paper at: http://instrumentation.co.za/+C15140
For more information contact RJ Programmable Techniques, +27 (0)11 781 0777, [email protected], www.rjprogtech.co.za
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