Dodging a Digital Data Disaster
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Since we started using digital video, we have been losing video. Hard drives fail; it is a fact of life. Thus, several methods of safeguarding recorded video data have been devised to minimize the impact of drive failure.
The most common method of protecting data on hard disks wasn’t primarily developed for that purpose. RAID, or redundant array of independent disks (originally “inexpensive” disks), was developed to provide large capacity storage devices in the days when drive space was very expensive, and individual drives were very small.
The concept was that a number of small drives could be grouped together and presented to an operating system as one large volume. In these days, drives were measured in megabytes. Gigabytes, and especially Terabytes, weren’t even familiar to most folks.
One of the byproducts of grouping these disks together was that you could also build a measure of security into the drive array, depending on how you wrote to the disks.
The simplest method of using RAID to protect your data is through drive mirroring. Mirroring is basically making an exact copy of one drive on another. Anytime data is written to the first drive, it is copied to the second. This is known as RAID level 1. RAID 1 is redundant for sure, but it does not offer much read/write performance, as it takes time to write to the second disk.
Another RAID method, striping, is used in RAID level 5. This has become a popular standard for video systems. Striping involves breaking the data up into small pieces, and spreading those pieces across multiple drives. Each drive, however, also contains some of the information from the other drives (a parity block). If any single drive fails, this redundant info can be pulled from the surviving drives and used to rebuild the failed one. This way, no video is lost in the case of one drive failing. If a second drive fails before the original is replaced and rebuilt, all video is lost.
Other RAID levels are becoming more popular, such as RAID 6, which is striping with dual parity. In other words, a RAID 6 system could survive the failure of two drives, whereas RAID 5 can only handle one. Also, RAID 10, or 1+0, uses a combination of striping and mirroring. This isn’t quite as popular for video archiving as RAID 5 and 6.
Blending Best of Old With the New
It remains to be seen if any network or digital product can replicate the stability and “bulletproof” perception of analog devices. Methods like those we’ve talked about can go far to ensure that your data or systems are as resilient as they can be given today’s digital world.
MCSE- and CCNA-certified Steve Payne has 15 years of industry experience, presently serving as a network/security system sales engineer and trainer for Warren Associates. He can be reached at [email protected].
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