Storage development and common technologies In the late 1990s, digital video monitoring based on digital signal processing (DSP) gradually became popular, and various codec technologies have been widely used in image processing. The processed images can also be transmitted in the form of digital code streams. The storage has also begun to enter the digital era. The most typical application is a digital hard disk recorder (DVR), which uses an internal hard disk for image storage. This storage method has fundamental changes in storage time, image retrieval, system maintenance, and remote recall. However, because most of the digital video surveillance systems at this stage have obvious localization characteristics and relatively small scale, storage also shows obvious front-end and stand-alone characteristics. In recent years, with the rapid development of information network technology, networked video surveillance systems that are centrally managed and controlled through a central business platform, with network video servers and IPCamera as the front end, have begun to be widely deployed. Due to a reasonable architecture, flexible expansion, and clear layers, network video surveillance can bring users a new security application experience, thus quickly becoming the main form of building a new generation of video surveillance systems. The distributed front-end and platform architecture, centralized management and control, and flexible and convenient user access have made the storage part of the network video surveillance system begin to be networked. Networked storage brings a new storage architecture to video surveillance. On the one hand, users are more flexible in storage deployment and access is simpler. On the other hand, it is also more convenient to build a video surveillance system that requires mass storage. DVR storage: internal storage of the codec-DVR storage is the most common storage mode at present. The codec device is directly connected to the hard disk, and currently it can bring up to 8 hard disks. However, due to the limitation of the performance of the codec equipment, the sequential write mode of the hard disk is generally adopted, and RAID redundancy technology is not applied to achieve data protection. With the continuous increase of hard disk capacity, the probability of single-chip hard disk failure leading to the loss of critical data is increasing synchronously, and the limitations of DVR performance also affect the sharing and analysis of image data. The characteristics of this method are: cheap, easy to use, can be operated through the remote control and keyboard; DVR mode is suitable for small-scale, distributed deployment. Domestic DVR products such as Haikang and Dahua's products are very mature. Codec + storage: Codec external storage device, connected through the codec's external storage interface, mainly using SATA, USB, iSCSI and NAS storage protocol expansion. In this way, the capacity of the codec can be further expanded, which is suitable for small and medium-scale deployments. The reliability of the surveillance video data is guaranteed by RAID technology. Among them, the direct connection mode adopted by the SATA / USB mode cannot be shared and has low expansion ability; the IP network (iSCSI and NAS) mode has better expansion ability and sharing ability. Haikang's DS series monitoring NAS storage products, and Bono Storage's SMI series storage products are all very mature in the monitoring industry. Centralized storage: The server connects to the front-end codec, downloads the data through a streaming media protocol, and then stores it on the storage device. The server and storage device can be connected through SCSI, iSCSI, NAS, FC protocol. The centralized storage method is suitable for the deployment of large and medium-sized platforms. In the centralized storage method, the IP connection mode (iSCSI, NAS) has good scalability and manageability, and has a high-performance price ratio. Three storage monitoring patterns First, the front-end storage pattern The so-called front-end storage is a built-in storage component in the front-end device of the network video surveillance system (such as a network video encoder or network camera), and the front-end device directly completes the local recording and storage of the surveillance image. Front-end storage has several advantages: First, it can reduce the capacity pressure brought by centralized storage through distributed storage deployment; Second, it can effectively relieve the network traffic pressure brought by centralized storage; Third, it can avoid centralized storage. The image is lost when the network fails. For front-end storage, since the number of monitoring points on a single front-end encoding device is usually not large and the storage time is not long, the storage capacity is not high. Network cameras generally use CF cards or SD cards, and video servers generally use built-in hard disks. This is basically the same as the previous stand-alone storage. What is essentially different from the previous stand-alone storage is that in order to ensure the flexibility and convenience of user access, all front-end storage in the network video surveillance system must provide point-to-point stand-alone access, but also be provided through a unified interface Centralized sharing of all content. To this end, the network video surveillance system performs unified management and scheduling of all front-end storage through a central business platform, and realizes the networking of storage space and storage content. In this way, users can directly log in to a single front-end device for on-demand playback of recorded materials, or log in to the central business platform for centralized retrieval and playback of all front-end recorded materials. Second, the central storage pattern In network video surveillance systems, more central storage is deployed. The front-end equipment collects the image of the monitoring point and encodes and compresses it into a digital monitoring code stream, and then transmits it to the central business platform through the network. The central business platform distributes the code stream to the network video recording unit for centralized storage. In many large-scale video surveillance networking applications, multi-level distributed central storage can also be used, that is, sub-central storage. This can reduce the pressure on storage capacity and network traffic brought by a centralized storage on the one hand. Greatly improve the reliability of the system. The use of central / sub-center storage has obvious advantages in the following aspects: first, it is more convenient for users to retrieve and call recording resources; second, it is easier to ensure the integrity of the stored content, not because of a front-end device Theft or damage leads to the loss of important content; third, it can reasonably schedule resources and allocate storage space for front-end equipment as needed, thereby saving resources; fourth, it is conducive to the development of diverse storage strategies to meet the personalized needs of users Fifth, it is easy to maintain, which is convenient for centralized detection and timely troubleshooting. For applications where the number of monitoring points is relatively small and the storage time requirement is not long, the central / sub-central storage can be deployed in a relatively simple way, such as server plug-in hard disk or external disk cabinet, called DAS (direct access storage), and Stand-alone is similar. With the widespread recognition of the advantages of network video surveillance, more and more large-scale or even super-large-scale video surveillance systems are beginning to appear, such as the social security monitoring system under construction of "Safe City", China Telecom and China Netcom are in full swing The "global eye" and "wide-view" two operational-level video surveillance systems, these surveillance systems are facing the need for large-scale access to front-end equipment and large-capacity centralized storage. In the past, stand-alone storage methods could not meet the application requirements of these systems in terms of flexible capacity expansion. More advanced network storage devices and storage technologies must be adopted, among which the typical ones are SAN, NAS, and iSCSI. SAN (storage area network) originated in the middle and late 1990s. Unlike DAS, SAN is based on Fibre Channel technology. Servers and storage arrays are connected by Fibre Channel switches to form a regional network dedicated to data storage. SAN uses a network-oriented storage structure, data processing and data storage are separated, with the characteristics of easy storage space expansion, flexible addressing, data transmission over long distances, high I / O performance, high utilization rate of storage equipment, etc. Storage architecture. Unlike SAN based on a special Fibre Channel protocol, NAS (Network Access Storage) implements the interconnection of servers and storage arrays based on IP networks, uses TCP / IP protocol for communication, and performs data transmission in file-level I / O. In contrast, the installation, commissioning, use, and management of NAS devices are simpler and the deployment costs are relatively low. iSCSI is a new standard protocol of IETF, that is, a transmission standard that converts SCSI block data into network packets through an IP network. It transmits data through an IP network like NAS, but in terms of data access methods , It uses the same BlockProtocol protocol that is different from NAS and the same as SAN. As a result, the value that iSCSI brings to users lies in: First, iSCSI makes it possible to transmit SCSI data packets over Ethernet, freeing the SAN from the expensive optical fiber network, and the original function can be realized through the IP network, which reduces the Management complexity reduces costs; second, due to the complexity of user application requirements, SAN and NAS storage networks are often deployed at the same time, and iSCSI can integrate the two. These characteristics of iSCSI are very suitable for the current status and direction of the development of video surveillance, especially in the field of operational-level video surveillance, where the storage scale is large and the investment is high. Based on the current mature IP network, the construction of central / sub-central storage systems Technology is undoubtedly a good reference. 3. Application storage pattern The storage network architectures commonly used in video surveillance systems include DAS, NAS, SAN, and IP-SAN. The types of storage devices commonly used include SCSI disk arrays, FC, and iSCSI devices. These devices are mature in technology, simple in structure, and easy to install and implement. However, these devices all have a common shortcoming, that is, the storage device can only play a simple data storage function in the video surveillance system, and cannot replace the server to run specific application software. A large number of dedicated servers are still required in the video surveillance system. In fact, with the rapid development of chip technology, the operation and processing speed of CPU or dedicated ASIC chips have increased exponentially, while the overall price of storage devices is continuously decreasing. In the selection and purchase of equipment, users generally choose a slightly higher-level storage device for the sake of equipment replacement. Furthermore, when the investment is ample, the price difference will have less impact on users. Therefore, in many application systems, the performance of storage devices purchased by users is often much higher than the actual requirements of actual business systems, and even exceeds several times. In some small and medium-sized video surveillance systems, the performance bottleneck in the system often appears on the video server instead of the storage device. The bandwidth provided by the storage device is often twice or three times the actual total bandwidth of the video surveillance. IOPS is also the actual demand. 3 to 5 times. The storage device controller is in a half-load working state for a long time, and a large amount of high-performance resources are wasted. In order to ensure high availability, efficiency, stability and security, the controller part of the storage device is generally specially designed, and uses a dedicated processor and cache, and its technical parameters and performance are higher than ordinary PC servers. In order to effectively utilize the surplus storage resources, special function application software can be embedded in the storage device controller. The storage device not only provides a data storage server for the system, but also provides a certain software application server. This storage device is called Application storage. Six ways to monitor and store Digital video surveillance involves the collection, storage, and use of huge amounts of data. Therefore, an efficient video surveillance system must have an efficient data storage system, which is related to the efficiency of data management, data security and data utilization efficiency. Then, in the telecommunication-level digital monitoring system, the requirements for the data storage system generally meet six requirements. One of the important features of the carrier-grade digital monitoring system is a large number of centralized data storage and decentralized front-end applications. Therefore, the storage system must have strong data transmission capabilities, otherwise it will affect the efficiency of data storage and utilization. The demand for massive data storage and the characteristics of rapid growth and change require that the storage system must be able to meet the massive storage requirements for telecom-level data monitoring, and at the same time must have good scalability to cope with the rapid increase in data volume for the expansion of storage space. In addition, since the monitoring system generally requires real-time video input, this real-time video input puts forward higher requirements on the data write ability of the disk array, otherwise, when the write speed cannot reach the requirements, the data is concentrated in the cache in large amounts , Will eventually cause the cache data to overflow and cause the host to crash. At present, surveillance video needs to delete data after a period of time. After the data is deleted, there will be a certain time interval. The data cannot be written immediately. At this time, the data is stored in the cache. Of the data stays in the cache, waiting for rewriting to the hard disk space. In addition, for the telecommunication level system, good stability is necessary, if lack of stability, it will cause great trouble to many users, and even bring huge losses. The huge storage requirements of carrier grade determine the requirements for good storage management. Simple and orderly management can help users reduce the cost of operation and maintenance, and is also an important guarantee for system stability. funcTIon ImgZoom (Id) // Re-set the image size to prevent the form from being broken {var w = $ (Id) .width; var m = 650; if (w <m) {return;} else {var h = $ (Id) .height; $ (Id) .height = parseInt (h * m / w); $ (Id) .width = m;}} window.onload = funcTIon () {var Imgs = $ ("content"). getElementsByTagName ( "img"); var i = 0; for (; i
19.5V Desk-top power supply were widely used in digital, LED lighting, stage lighting, security, home appliances and
other products, is the most widely used in the electronics industry. Normally, there are 3 different kinds of AC socket for a
Desktop Power Adapter – they are C6 AC socket, C8 AC socket and C14 AC socket. What
you need is to choose the right AC plug for your country, then the desktop
adapter can be suit for any countries.
All our AC/DC power adapters were get through 100%
full-load burning test for at least 2 hours, and 3000Vac withstanding voltage
test for 1 minutes. The conversion rate of our desktop power supplies is 85%, which
is much higher than other factories.
19.5V Desktop Switching Power Supply 19.5V Desktop Switching Power Supply,Desktop Switching Power Supply,19.5V Switching Power Supply Shenzhen Juyuanhai Electronic Co., Ltd. , https://www.powersupplycn.com
Three patterns and six methods of video surveillance storage
The development of storage in the field of video surveillance is closely related to the development of video surveillance itself. The collection, transmission and display of images in analog video surveillance are based on analog devices, and the storage of images is also based on analog devices, namely video tape recorders (VCRs). Due to the use of video tapes, on the one hand, the storage capacity is greatly limited, on the other hand, image retrieval is very cumbersome, and remote calling cannot be achieved. In addition, there are obvious defects in terms of preservation time and system maintenance.