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Possible Duplicate:
Are tape archives still used?

Possible Duplicate:
What lasts longer: Data stored on non-volatile flash RAM, optical media, or magnetic disk?

A lot of the backups done at my work are done to tape. Frankly, I was surprised tape was still being used in a production environment, where the hard disk rules the storage market. This got me wondering WHY people are still using tape for things like backups.

Is it because of the cost? I would imagine that they cost more than hard disks due to there being a lower demand. Are they better/easier to store?

Or is it just because they don't want to upgrade to a newer technology?

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nopcorn
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2 Answers2

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One reason and one reason only: longevity.

Hard disks and solid state drives do not have a long lifespan as compared to conventional tape-storage media. I cover some of the reasons why SSDs and HDDs wear down over time here, but the basic idea is that with tape backups, there is next to no data corruption over time, and an extremely low chance of mechanical failure. Even if the tape did happen to run off the spool, it would be much easier (and less risky) to move the tape to a new "cassette" - the same cannot be said for replacing HDD platters, which is not a task for the faint at heart.

Do note that the tapes themselves have a limited number of writes, so they are also not written to as frequently as hard drives. Finally, tapes are used primarily for archiving purposes only - they are usually written to once, and then kept in a climate-controlled storage facility until they are (ever) needed. For this purpose, tapes are great - they are light, cheap, and easy to replace.

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Breakthrough
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Tape is not as sensitive to drops, bumps, or handling-cause issues that plague hard drives. They also offer a relatively low cost per gigabyte, compact size, and decently high speed. Hard drives, because they constructed of glass or ceramic disks and many movable parts, in addition to expected data degradation over time, are simply not up to the task of archival storage.

That said, most enterprises use multiple levels of backup, including both various arrays of hard disks working in combination with tape backups.

Hard disks offer fast backup and recovery as well as easy single-file restores. Tapes offer long-term archival storage, ease of off-site transfer and storage, large capacity, and small size.

Their differences do not point to a general winner overall, but each have their strengths and make them appropriate for specific purposes and strategies.

In my office we have incremental backup over WAN for easy and fast, single-file and point-in-time restores at user request, and tapes that are shipped off-site on a rotating schedule based on nightly backups.

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