In a video surveillance system, what storage solution is selected directly determines the system architecture of the entire system as well as the performance and stability of the system. Currently, there are roughly two storage solutions in video surveillance systems. One storage solution for the video surveillance system is to use a DVR device with a certain storage capacity (such as 1.2T) at the front end of the camera surveillance. All the required data is stored in the front-end DVR storage device. Maintain and maintain multiple DVR devices, including the storage data of these DVR devices, such as video storage, deletion, and playback. In this scheme, all data is mainly stored in the DVR, and the background is mainly responsible for maintenance and necessary storage.
The other is to use a DVR or network video server in the front end of the camera monitoring, and the storage is mainly stored at the remote end through the background PC or server software to save the data on the background storage device.
Both of the above storage solutions have many disadvantages, especially when there are many monitoring points and the required storage capacity is large. These possible disadvantages include: Difficult to maintain due to storage dispersion; due to low storage professionalism Reliability is not high, which leads to low reliability of the entire system; storage utilization rate is not high; storage scalability is not good.
In order to overcome these drawbacks, it is recommended to use IPSAN based on distributed storage, centralized management, and iSCSI technology as the storage solution for video surveillance. The main features of this solution include:
1. Distributed storage and centralized management;
2. IPSAN (STorageAreaNetwork) based on iSCSI technology;
3. The streaming media gateway can be used as the core device of the storage solution.
Distributed storage, centralized management In this solution, there are three levels:
1. Superior monitoring center: There is usually only one superior monitoring center, mainly composed of digital matrix, authentication server and VSTARClerk software.
2. Local monitoring center: There can be multiple local monitoring centers, which can be set according to geographical location or according to administrative affiliation, which is mainly composed of digital matrix, streaming media gateway, iSCSI storage equipment, VSTARRecorder software, etc .; audio and video data are all Mainly stored in the local monitoring center, this is the concept of distributed storage.
3. Surveillance front end: mainly composed of cameras and network video servers. Among them, the VE4000 series network video servers can be equipped with hard disks. The hard disks are mainly used for temporarily storing audio and video data when the network is poor, or need to save some Important data.
The storage device of the local monitoring center can also use a server with a SCSI disk array. However, due to the limited network sending and receiving performance of the server, which affects the performance of the entire storage system, it is recommended to choose a professional iSCSI storage device.
IPSAN based on iSCSI technology
Introduction to iSCSI principles
This is a new Internet protocol based on a storage network developed by the IETF. Its principle is to transmit SCSI commands through an IP network, which makes it easier to transfer data on the network and achieve remote storage management.
iSCSI enables standard SCSI commands to be transferred between the host system (initiator, IniTIator) and storage device (target) on the TCP / IP network, and the iSCSI protocol supports the transfer of standard SCSI commands between systems. The connection between the systems is achieved through the standard IP network infrastructure. The working principle of iSCSI is that when an end user or application (initiator) sends a request, the operating system will generate an appropriate SCSI command and data request. , SCSI commands are encapsulated to perform encryption processing when encryption is required. These commands plus TCP / IP protocol headers can be transmitted over Ethernet. After receiving the data packet, the receiving end (target) unpacks it in the opposite direction, parses out the SCSI command and data request, and then sends the SCSI command to the SCSI storage device driver. Because iSCSI is a two-way protocol, it can Return the data to the original request.
Network storage solution based on IPSAN
In this solution, the network video server needs to support the iSCSI protocol, which is the initiator, and the iSCSI storage device located in the monitoring center is the target. The iSCSI storage device of the local monitoring center can serve as the storage device of multiple network video servers, and the iSCSI storage device can also be externally attached with a tape device to further expand the storage capacity.
Network storage solution with streaming media gateway
In the network storage solution, each network video server occupies an IP. If you want to perform remote monitoring through the Internet, the IP address of the network video server must be a public IP. In general, public IP addresses are rare resources. In addition, remote monitoring is affected by network capacity restrictions and network congestion. Bandwidth is usually not guaranteed, which brings inconvenience to remote monitoring, and now there is a streaming media gateway on the market that can solve these two problems.
The streaming media gateway is an embedded hardware device. All message forwarding is based on hardware forwarding (if it is software forwarding, the performance cannot meet the requirements), and the forwarding capability can reach more than 1Gbps. The main functions of the streaming media gateway include:
1. Support NAT conversion function;
2. Support video distribution function. When multiple remote monitoring users access the same network video server, they all need to send a request to the streaming media gateway, and then the streaming media gateway sends a request to the network video server. When the streaming media gateway receives After the data of the network video server (note that there is only one data stream between the video server and the streaming media gateway), it is responsible for distribution to multiple remote monitoring users;
3. Support video on demand service, remote users can complete the video on demand function through the streaming media gateway;
4. IniTIator supporting iSCSI.
The above functional streaming media gateways can also be configured separately.
Conclusion
In the current video surveillance system, the performance and reliability of the video surveillance system are degraded due to the limitations of the storage solution, which always troubles us. The IPSAN storage solution based on iSCSI is undoubtedly a good solution to the storage problem, especially when iSCSI When the performance of storage devices continues to increase and prices continue to decrease, this method is even more inevitable. It is believed that storage solutions based on iSCSI technology will gradually become the mainstream of storage technology in large-scale network video surveillance.
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