For the monitoring project, we need to consider four parts: front-end system, transmission system, storage system and display system. For the transmission system, we have mentioned many times before, and the storage system is a very important part of the monitoring project. Today, let’s talk about the knowledge of video image storage.
1、 IP-SAN storage
IP-SAN, that is, the SAN storage architecture based on IP Ethernet, uses iSCSI protocol to transmit data and store it directly on the IP network. ISCSI protocol is to transmit SCSI command packets in TCP / IP packets, that is, scsiortcp / IP.
IPSAN is also a kind of San, but the server and storage are interconnected through network switches. The performance is not the best, but it is not limited by distance. IP storage is widely used and can also be used as large-scale monitoring storage.
IP-SAN can divide the storage device into one or more volumes and export them to the front-end application client. The client computer can create a new file system (format) for these imported volumes. The access mode of client computers to these volumes is device level block access. IP-SAN divides data into multiple data blocks and writes / reads data to / from disks in parallel. The characteristics of block level access determine the high I / O performance and low transmission delay of iSCSI data access.
In short, it is stored in blocks. You can think of it as a hard disk with array function, which is actually disk array + hard disk.
We can see the following topology diagram:
Compared with NVR storage, IP SAN is generally used with streaming media server.
The function of streaming media server is to effectively solve the problem of repeated occupation of network bandwidth when multiple users access the same real-time video data information at the same time, fully save network bandwidth resources and effectively reduce the occurrence of network congestion. A streaming media server needs to be equipped in the network monitoring center.
IP-SAN storage mode has the following characteristics:
1. It has the advantage of high bandwidth “block” data transmission.
2. Based on TCP / IP, IP network technology is mature and has all the advantages of TCP / IP, such as reliable transmission, routability, etc., reducing the complexity of configuration, maintenance and management.
3. ISCSI storage network can be deployed through Ethernet, which is easy to deploy and low cost.
4. It is easy to expand. When the storage space needs to be increased, it can be fully met only by adding storage devices, with high scalability.
5. Data migration and remote mirroring are easy. As long as the network bandwidth is supported, there is basically no distance limit, and better support backup and remote disaster recovery.
2、 CVR storage
Haikang CVR storage mode can support the video to be directly written to the storage device through the encoder, save the cost of the storage server, avoid the single point of failure and performance bottleneck of the server, and the unique data structure ensures the high stability and high performance of the monitoring service.
CVR is a special video storage device for security monitoring. CVR rewrites the video stream on TCP / IP into a stream data structure and writes it directly to the disk, so there are no files and fragments stored in the disk.
Characteristics of CVR storage mode
1. Front end direct write unified management
Haikang CVR storage mode can support video to be written directly to the storage device through the encoder, eliminating the storage server. Centralized management and status monitoring of multiple network storage devices can be realized through the centralized management platform; It can realize the centralized configuration and management of storage devices in the business system, and monitor the working status of storage device units and their corresponding manageable device components, operation protocols, raid groups, etc. in real time; Centralized alarm management supports regular status inspection of storage devices, and real-time monitoring and centralized display of system operation status, array operation, iSCSI, HTTP, CIFS, SCSI channel and other status.
2. Simplify network structure
Haikang CVR storage mode is directly written into the storage device through the front-end coding device, which does not need the storage server, simplifies the network structure, and liberates the network pressure between the storage server and the storage device in the original design.
3. Unique streaming media file system protection technology
Haikang CVR storage mode adopts unique vspp video stream pre protection technology to completely solve the problems of monitoring service stop, data read-only or loss caused by file system instability or even file system damage caused by power failure and network disconnection.
Haikang CVR storage mode adopts its own unique data block management structure and fault-tolerant mechanism to break away from the dependence on the server-side file system, avoid the impact of file system damage on the monitoring business system, and provide a more stable and efficient management mode.
4. Efficient disk fragment immune technology
Haikang CVR storage mode adopts the combination of disk pre allocation and delay allocation technology. Firstly, it is used to find the free space area and store new data, so as to maximize the system performance and avoid disk fragmentation. At the same time, combined with efficient defragmentation program, defragment the disk when the system is idle to improve the performance of the system.
3、 NVR storage
NVR is the abbreviation of network hard disk video recorder. The main function of NVR is to receive the digital video code stream transmitted by IPC (network camera) equipment through the network, store and manage it, so as to realize the distributed architecture advantages brought by networking. In short, through NVR, you can watch, browse, playback, manage and store multiple webcams at the same time. Get rid of the shackles of computer hardware and no longer have to face the cumbersome task of installing software.
Now there are a small number of 128 channel NVRs in the market, because NVR is x86 architecture storage + monitoring software, and it also has disk array function.
NVR is mainly used in small and medium-sized monitoring schemes. However, for large-scale monitoring applications, NVR’s short board outweighs its advantages. Many monitoring points, large code stream, high pressure and large capacity will make it unable to use. For large-scale public monitoring, its scalability and manageability should be considered, so ipsna or CVR storage mode is adopted.
4、 Application Comparison of three storage methods
1. Comparison between NVR and IP SAN
NVR mostly belongs to front-end deployment and edge storage. IP SAN belongs to central computer room storage, which is suitable for full centralized or decentralized centralized storage;
In the field of HD monitoring, IP-SAN focuses more on large-scale networked data storage in special industries. This technology not only has strong centralized solution ability, but also has corresponding performance in long-distance transmission and management.
IP SAN supports multiple RAID levels: 0, 1, 0 + 1, 3 and 5. In most cases, arena company recommends using RAID5 because RAID5 has high hard disk utilization and is a RAID level with high security. In addition to RAID level protection, it can also provide multiple global hot backup disks. Once any disk in the array has a problem, the global hot backup disk will work immediately to protect data.
2. Comparison between IP SAN and CVR
The CVR front end writes directly to the storage with the streaming media protocol without network mounting, and CVR takes the initiative to fetch the stream; In IPSAN mode, each front end mounts independent iSCSI storage space, which is uniformly allocated by the management server;
CVR does not rely on any intermediate link, and IPSAN relies on an intermediate management server.
When the CVR network is poor, you only need to try to establish a session connection, and the reconnection process takes a very short time; IPSAN is easy to cause connection interruption due to poor network. Constantly trying to re mount the connection between the front end and storage is time-consuming and easy to lose video.
IPSAN can be used not only in security monitoring, but also in computer storage. CVR is a special video storage device for security monitoring.