Digital Video--The Other Type Of Data.

Fortune 500 corporations, government agencies, airports, and organizations across industries worldwide, along with entire consumer communities, are increasingly accepting digital technology as a daily aspect of their lives.

Digital business data, however, is no longer limited to traditional text data. Video is increasingly becoming the other type of data that many corporations are turning their attention towards. Their interest is generated by the fact that, by integrating video with traditional business transaction data, management teams are now able to expeditiously accomplish tasks never before possible.

This increasing acceptance of digital video presents interesting challenges to IT departments. Fortunately, large-scale storage and networking technologies are promptly coming to the rescue. Manufacturers of networked digital video management systems (NDVMS) are paying close attention to the advances made in Storage Area Networks (SANs) and high-speed networks. These technologies provide the storage-management solution demanded by the high-speed access and long-term storage of video data.

Digital Video And Traditional Business Data

To understand the challenge video presents to IT departments, you need to understand the differences between digital video and traditional business data. Traditional business data, such as email, word processing documents, and database transactions, tend to be relatively small and transfer across a network in occasional bursts. If errors occur during transmission, the data can be retransmitted without adversely affecting other users on the network.

Digital video data, on the other hand, is typically large, continuous, and not very tolerant of timing errors. Transferring this type of data across a packet-switched network like Ethernet will often result in degraded performance for other users on the network because it quickly saturates the network's bandwidth. In addition, a saturated network makes it almost impossible to retransmit data if an error occurs. For organizations that rely on video data, such as a security team in an international airport, losing this data can quickly result in disaster.

One way to reduce the impact of transmitting digital video data is to compress it at the source. NDVMS manufacturers are currently using technologies like MPEG and Wavelet compression to reduce the size of the data before it is transferred across a network. But compression alone isn't enough to completely eliminate the problems of managing digital video data. A robust network, data buffering, and high-performance storage management solutions are needed too.

Digital Video Networks

For the network administrator in an IT organization, the addition of digital video data to a network infrastructure needs to be carefully planned. The location of digital video sources on an existing network needs to be analyzed to determine if the video source will impact other users. This is especially critical if the video is being transmitted over a WAN or the Internet. Once the planning stage is complete, network administrators can then decide the best way to solve any bandwidth problems.

One solution to bandwidth problems is to isolate digital video sources on separate network segments so that users are not impacted by the heavy demands of the video data. High-quality network components should be used to minimize network errors, and these components should be tuned for maximum throughput. For organizations that require extremely high bandwidth, other network technologies such as ATM should be considered, which are geared toward large-volume data like digital video.

Buffering Digital Video Data

Even with a solid network foundation in place, digital video data can still be lost if a transmission error occurs or bandwidth is suddenly reduced. NDVMS manufacturers often buffer video data at the source and destination to allow data to be retransmitted, and to handle network timing delays so video playback is smooth. In addition, some systems use data buffering along with sophisticated "pacing" algorithms to balance the load from multiple video sources, which helps to reduce network traffic and keeps storage devices, such as tape drives, from being overwhelmed with data.

For example, an integrated NDVMS takes data from a video source, such as an analog camera, compresses it, and writes it to a hard disk. Then a separate process transfers the data from the hard disk over a network to a storage management sub-system. Each component in the NDVMS communicates with other components to allow for data retransmission, and to balance the load from all video sources for optimum performance of the entire system.

Even with intelligent-load balancing algorithms, it is still important to properly specify the system requirements. If there are not enough storage servers and tape drives to quickly store the data, and there are too many digital video feeds, eventually the buffer disks would fill up and data would be lost.

Digital Video Storage Management

It isn't enough to have a fast network and data buffering if the storage solution used to store video data degrades performance or loses data. For organizations deploying digital video solutions, high-performance storage technologies are needed to handle the large volume of data. IT departments using traditional software to back up their databases, for example, will likely find that the addition of digital video to their backup program will overwhelm their storage systems. During a backup of a database server, the server sends data across a network to another computer that has a tape drive attached. This creates a load within the database server--because it must move data from its hard disk to the network--and a load on the network itself due to the large amount of data. The combination of these loads can create performance problems for users who want to use the database when a backup is occurring.

Fortunately, the growth in business data across the enterprise is driving new storage technology solutions that also benefit digital video data. As indicated earlier, storage technologies such as automated tape libraries, and particularly SANs, are enabling the deployment of digital video applications across industries as never before. Storage Area Networks help solve the performance problems when storing large amounts of data. The SAN does this by separating the network and computers used to back up data from the rest of the network. In addition, specialized SAN hardware helps reduce the load inside a server by transferring data directly from the server's hard disk to the Storage Area Network without using the server's CPU and bus (See Fig).

Another benefit of SANs is that as an organization's storage needs grow, additional tape libraries and backup servers can be added to the SAN without massive changes to the network. All these benefits for storing traditional business data also help digital video data.

Steve Kelleher is a senior system software engineer at Loronix Information Systems (Durango, CO).