The application of video server in broadband network

As the core equipment of VOD system, video server has appeared in recent years from PC-level small Video server to the development trend of large video server based on parallel processing structure, many vendors claim its video server processing ability is powerful, how flexible the network mode, how the system scalability is superior. For operators, how to choose the right video server and the corresponding VOD solution becomes a more prominent problem. As the core equipment of VOD system, the choice of video server determines the quality of the whole system solution to a great extent.

At present, the main video server manufacturers are from the United States, more well-known manufacturers have Ncube company, with NCUBE3 (has discontinued) and NCUBE4 series of products, the United States parallel computer company Mediahawk, HP company MediaStream series, ETC., The servers for these companies are designed specifically for streaming media applications. In addition, the SGI Company's origin2000,3000 series, SUN's SPARC,HP company's HP9000,IBM company rs/6000, and other general-purpose architecture computers, used primarily for high-performance business computing, rather than dedicated streaming media applications, However, it can also be used as a video server for streaming media application development on its platform. In the face of many choices, the following factors can be used as a basis for your decision making.

One, the storage of the media data

VOD system needs to store a large amount of media content data, need a lot of storage space, to 6mbit/s MPEG2 transmission flow to calculate, hourly program needs 2.51gbit/s disk space, a 300-hour program capacity of the system requires nearly 760gbit/s actual file storage space, Considering the cost of the file system itself and system fault-tolerant considerations, the actual capacity demand will be more, the large capacity data storage needs the system to have the good fault-tolerant performance, and has the sufficient stability, when some data errors occur, the system can restore and reconstruct the data online without affecting the normal operation of the system.

In order to ensure the storage security of mass media data, the system is stable, and has a certain fault-tolerant performance, using streaming media file system and operating system file isolation mode, this is similar to the concept of SAN (storage Area Network), and the streaming media file is raid protected. The raid level is typically a RAID level that is currently used more than RAID3 or RAID 5.

The storage mode of media data is an important index to evaluate streaming media service system. The safer way is to use the system separate way, that is, with the video server operating system completely separate way, the benefits of this approach is easy to maintain, but also easy to upgrade the operation system, in the operation system is paralyzed, just reinstall the operating system, Media data does not need to be redesigned, which greatly reduces the average system recovery time (MTTR), and most video server companies, such as Ncube, SGI, and concurrent, use this approach.

The implementation of RAID mode has two kinds of hardware and software, for software RAID implementation way, need to occupy a part of storage I/O resources. But hardware RAID mode requires a high upgrade cost for storage expansion, and software RAID upgrades cost less when storage expands, and the Ncube company's video server uses software RAID mode.

Ii. input and Output interface type

The main features of video server interface are: Multiple storage i/o+ multiple network I/O.

Storage I/O is typically ultra SCSI, ULTRA2 SCSI, ULTRA3 SCSI, or fiber Channel, typically with one disk array per SCSI or FC channel, and storage I/O capability is all SCSI or FC channel I when the system is fully resource-sharing The sum of the/O rate.

For network I/O, the General video server has Ethernet (10/100m) interface, some servers have 1000mbit/s Ethernet interface, can be used for streaming media applications on the LAN, but mainly used for communication with the control system, such video server can only be used for local applications, And can only be used for streaming media applications based on IP mode. At present, due to the progress of Ethernet technology, IP over SDH and IP over DWDM technologies such as the mature, LAN and man, the difference between the gradual disappearance of IP streaming media can easily be a large application in man, so currently provides 10/100BASET,GBE, 10GbE network interface has become the video server to keep up with the trend of the Times performance.

Currently, there are many streaming media services that are based on a CATV network or a HFC network, so many servers provide Dvb-asi or qam64/256 interfaces for such an access network. In addition, for ADSL access mode, some servers can provide ATM oc-3 or OC-12 interface to provide high-speed data access to the local dslam.

Network I/O is generally provided by the service module on the server, the video server's video output capability is computed by the I/O interface of the video stream, and the total output capability is the sum of the I/O interface rate of all these video streams.

For video server I/O, an important metric must be met: The total effective storage I/O rate is greater than the sum of network I/O rates, where effective storage I/O refers to the actual storage I/O for media data, and the network I/O rate is the network interface used to advertise video streams.