Tape It to the Limit

By Davis D. Janowski  |  Posted 2003-03-11

Tape It to the Limit

Johns Manville—a Denver-based manufacturer of building materials, in business since 1858—has 52 facilities of varying sizes spread over North America, Europe, and China. With more than $2 billion in annual sales, 9,000 employees, and some 120 servers in its corporate headquarters alone, Johns Manville gives top priority to data backup every night.

Scott Blancett, a manager in the IT department, knew the companys ever-growing backup needs were crying out for a bigger and better solution than the three-year-old StorageTek DLT 8000–based libraries. So Johns Mansville took Hewlett-Packards new second-generation LTO (Linear Tape–Open) product, the HP Ultrium 460e, for a test-drive.

"The backup speed is really tremendous," Blancett says. "Much faster than our old DLT 8000 systems."

This observation made Blancetts decision to replace the companys backup hardware a no-brainer. He wants to buy automated, multitape libraries containing the 460e drives later this year. With these, the company will need fewer machines to do the job.

"Believe it or not," says Blancett, "the cost, including three years of maintenance and support, will come out being less than paying for another three years of support and maintenance on our DLT 8000 machines."

An Ocean of Data

An Ocean of Data

After 50 years, tape remains the king of backup technologies, and manufacturers continue to make tremendous strides in improving their products. Even with the promise of better, more economical technologies for hard drives and optical backup on the horizon, tape will remain the backup medium of choice for the near term.

What we refer to as tape backup started out as a cumbersome, reel-to-reel system. But today, the tape media are self-contained cassettes in different shapes, sizes, and capacities from many manufacturers. And choices abound: From 1998 to 2001, nine new formats were introduced, adding to the dozen or more already in existence, according to research firm Gartner.

Tape Formats

Tape Formats

This story focuses on the midrange tape market, which targets small to midsize businesses with up to 400 employees. Two tape technology standards, Linear Tape–Open (LTO) and Super Digital Linear Tape (SDLT), dominate the market. A third technology weve reviewed in this story is Sonys AIT-3 format, which has a small but growing market share and interests us with its very high file restoration speed. Both LTO and SDLT technologies use similar-size square, one-reel cassettes with half-inch-wide tape. Smaller, rectangular AIT-3 cassettes use two reels and 8-mm-wide tape.

The LTO standard was created in 1998 by HP, IBM, and Seagate Technology, each of which makes drives that can use any manufacturers LTO cassettes. First-generation LTO cassettes have a raw or native data capacity of 100GB and a compressed capacity of 200GB.

HP started shipping the first drives and automated solutions for second-generation LTO in November 2002. This format has double the capacity—200GB native and 400GB compressed—and provides unparalleled read/write speeds. But attaining these speeds requires a fairly sophisticated network, with high-speed connections between your hardware, and also depends on the types of data being backed up and the speed of the hard drives holding that data.

SDLT 320 is the latest advance in Quantum Corp.s venerable DLT technology. It has the advantage of backward read compatibility, meaning it can read older DLT formats. SDLT 320 has a capacity of 160GB native and 320GB compressed.

Sonys AIT-3 technology has grown in popularity because of its smaller, thinner cassettes, which result in tape libraries that take up a mere 1U of rack space. AIT-3 has a capacity of 100GB native and 260GB compressed. Though it restores files quickly, it performs backup operations much more slowly than the other formats.

The most obvious difference among the formats is how data file locations and other drive-specific information are stored. LTO and AIT-3 cassettes both have on-board chips that store tape-specific information. While the original LTO Ultrium 1 specification allowed data location information to be stored on these chips, none of the manufacturers built this technology into their drives.

LTO and SDLT drives must read the beginning of a tape to determine where files are stored. So far, LTO chips have been used exclusively to store drive-specific information, such as which company manufactured the drive and technical details about proprietary drive functions. But AIT-3 realizes its extraordinarily high restore speeds from the contents information stored on its chips. Each technology has advantages and disadvantages, but during our testing, the relatively similar performances of LTO and SDLT drives proved the differences between them to be negligible.

When selecting a format, remember the bottom line, and not just in terms of hardware. Depending on the format, each tape can cost from $60 (AIT-3) to $100 (LTO and SDLT). IT managers and administrators must keep in mind that depending on their backup schedule, a years worth of media cartridges can end up costing more than the hardware.

Drives, Autoloaders, Libraries, and


Drives, Autoloaders, Libraries, and Software

A standalone tape drive can write to or read from one tape at a time. Autoloaders and small libraries are roughly analogous to jukeboxes or carousels handling multiple audio CDs. This type of device holds multiple tapes and uses robotic mechanisms to load and remove them from the enclosed drive, but still it can only write to or read from one tape at a time.

Autoloaders and libraries are about convenience; a user with a single-tape drive would have to insert one or more tapes every day by hand. But a user with an autoloader can just fill it with properly labeled tapes and walk away, maybe for weeks at a time.

The distinctions between autoloaders and libraries are rather blurry, even within the industry. An autoloader tends to have a single drive, while a library may have more. StorageTek, with its L20, L40, and L80 libraries, has gone even farther by engineering those devices to accommodate multiple tape formats. Libraries are generally considered more complex devices and tend to have more advanced features, such as bar code readers for keeping track of tapes, and they can hold more tapes. In fact, some large enterprise libraries can hold hundreds of tapes.

Unlike many other types of computer hardware, tape backup systems have evolved little in terms of native intelligence. This means they depend totally on software running on locally or remotely connected workstations or servers to carry out all functions. For an overview of the three most popular software solutions, see "Backup Software".

Final Considerations

Final Considerations

The choice of a format and device type depends on many factors, including the kinds of data you need to back up, the range of file sizes, the daily volume, and the quantity and speed of the hard drives youll back up from. If you have excessive data and a small backup time window, LTO or SDLT may be the best solution. If you need to restore files frequently, AIT-3 may be the answer.

Weve reviewed five external single-tape drives and five automated products for small to midsize businesses. The standalone drives range in price from $4,225 to $5,775, while the automated solutions range from $7,500 to $13,000. AIT-3, LTO, and SDLT products are all represented in both the single-drive and automated-device categories.

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