Magazine Article | December 1, 2001

RAID - Your Neighborhood Video Store

Source: Field Technologies Magazine

For data-intensive streaming video applications, RAID (redundant array of independent disks) can handle the incoming load, as well as offer online retrieval.

Integrated Solutions, December 2001

The contributions of RAID (redundant array of independent disks) tend to go unnoticed by desktop users. When the correct data appears in a timely fashion, users don't usually stop to applaud the efforts of unseen network storage resources, such as RAID. Ironically, RAID configurations make particularly valuable contributions to delivering data that is highly visible in nature - digital images. Because it provides online access and redundancy, RAID is a good choice for fast, reliable delivery of large, data-intensive video files.

Making And Saving Your Corporate Movies
The demand for video archiving has traditionally come from the film and broadcasting industries. Instead of pulling tapes of file footage, broadcasting companies, for instance, are increasingly using digital images to deliver time-sensitive programming. In the case of news broadcasts, digital images residing in large data files must be transmitted without interruption. Stored digital images also become company assets that can be exchanged with advertisers and other broadcasting entities.

Beyond the world of film and broadcasting, other sectors are increasingly interested in storing and accessing video. To retain visual as well as paper records of company announcements and policies, corporate enterprises are beginning to archive digital versions of videotaped events, such as annual shareholders meetings or employee training sessions. The potential for a prolonged slowdown in corporate travel may have companies increasing their use of Web casts and videoconferencing, two additional kinds of digital assets to be protected.

Having digital data online in a RAID array allows companies to conveniently search, move, and manipulate the data. Attached to each image file is a file of metadata, or source information about the video, such as when and where it was filmed and by whom. According to Bill Hartman, VP of marketing and business development for Ciprico (Minneapolis), metadata residing on a RAID array makes the video information accessible to data mining applications. "Metadata allows people to search for information that can tell them whether or not they need to retrieve and review the actual video. This reduces the time spent on searching the digital image files to find relevant pieces of film," Hartman says.

Hartman also points to the usefulness of large capacity RAID arrays for capturing digital images as they are being transmitted. Applications in which information is being downloaded from a satellite, common to government and the entertainment industry, are particularly reliant on fast storage processing. "The satellite is dumping huge amounts of information, but it's only in range overhead for a short period of time," Hartman explains. "Your storage system can't say, 'Wait a minute. I can't keep up.' That information can't be recreated. If you miss it, it's gone, so the speed and reliability of storage are crucial."

Safeguarding Your Video Assets
Advances in error correcting technology built into RAID devices can guard against interruptions in the data stream for digital images. Because they stall moving images, such interruptions are potentially more noticeable and aggravating than delays in text-based file retrieval.

Don Naples, VP of sales and marketing for RAID controller manufacturer Infortrend Corp. (Santa Rosa, CA), emphasizes the importance of tools that enable system administers to address drive problems in advance of actual drive failures. Drive cloning, in particular, allows administrators to clone the data on a drive that is beginning to show signs of problems. That data is placed on a spare drive while work is done on the problem drive. Cloning is particularly valuable in RAID 3 or RAID 5 parity configurations, which can handle single-drive failures but not simultaneous failures of two drives. "Cloning a drive doesn't eliminate the failure. But, by providing instant data convergence, it reduces the possibility that a second drive will fail before you can get your data back from the first failed drive," Naples says. "Cloning a drive also eliminates the process of rebuilding data based on parity information - a process that slows performance." According to Naples, drive manufacturers are already incorporating the kinds of alerting and reporting tools that enable drive cloning.

Finally, Hartman offers additional good news for enterprises looking to build storage systems that can handle video assets. "Corporations may be able to leverage their existing LAN or WAN (wide area network) infrastructure," Hartman affirms. "Corporate customers typically have high bandwidth on their networks, so doing high performance streaming is probably already supported by what they have in place."

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