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Wherein lies the fault?
Generally, users appear to be satisfied with their tape vendors. Rating the major tape brands, the brand that garnered the most users, Fujifilm, also snared some of the highest marks, with slightly more than 50% of respondents rating it very good or excellent. Imation ranked second, less than two percentage points behind, followed by Sony and HP. A few brands received poor or not very good ratings from more than 10% of respondents, with Certance LLC and Exabyte Corp. garnering the highest negative ratings at 16.7% and 16.2%, respectively (see Figure 9, this page).

Tape vendors boast of their quality control efforts. While they acknowledge occasional lapses, they say they're few and far between and generally affect a small number of tapes. Vendors cite mishandling of tape cartridges by users as well as distributors who sometimes pack their wares inappropriately before shipping them to customers. "Our overall rate of return is about .1%," says Fujifilm's Gadomski. This figure covers defective tapes as well as cartridges customers return when they've ordered the wrong product.

Overuse may also be at the root of some tape reliability issues. Vendors provide two durability ratings for their products. Shelf life is measured in years--typically 15 to 30 years--and reflects how long you can expect the media to retain its data and stay in good enough physical condition to be loaded into a drive and read. The second rating is essentially how long you should use the tape before retiring it to an archive. The way vendors define that rating varies, and may be expressed in terms such as uses or head passes.

"I have about 2,000 or 2,500 tapes under management in the library, most of which are in the 200 to 300 mounts category and some are below that," says CareGroup's Passe. "The upper end is in the 500 to 800 mount category."

Chris Caprio, technical service manager at Imation, notes that tape longevity depends on the tape technology in use. He adds that handling of tapes is "the biggest issue with determining media longevity and media performance." But Caprio doesn't see overuse as a major problem. "For the most part, customers understand that tape is really not a commodity" given the data it holds, so they tend to observe usage specifications.

A little more than 57% of respondents indicate that they monitor how often a tape is used. But vendor usage recommendations may not always be heeded. Twenty-two percent of respondents said they use a tape for more than 500 mounts before retiring it, while 26.5% said they err on the side of caution and retire tapes after fewer than 100 mounts. "I replace tapes every year," said one user, "and each one only gets used 26 times."

Using a tape 26 times may be overly prudent, but that kind of talk is music to tape vendors' ears. Mark Eastman, product marketing manager for Quantum Corp.'s storage division, says his firm recommends 200 uses for its DLT and SDLT cartridges; a use is defined as "a full write of the cartridge and a full read of the cartridge," according to Eastman. Despite their recommendations, Eastman says Quantum "typically finds that users just use the media until it dies." Many users may rely on the tape's sensors to signal when a tape is approaching the end of its road, he notes, adding that applications such as Quantum's DLTSage can help to track tape use and determine when a tape is approaching the end of its usefulness.

For mainframe environments, Fujifilm's Gadomski says system software does a good job of monitoring the useful life of a tape; when it records an unusual number of read/write errors it ejects the tape. For open systems, Fujifilm recommends about 5,000 head passes for DDS cartridges before retiring a tape, but Gadomski says tapes aren't typically used that long. Because they use linear scanning technology, LTO and DLT cartridges can typically handle a million or more passes, according to Gadomski.

Some tape vendors will analyze returned tapes to determine the precise cause of failure. Users are often willing to comply, but sometimes there will be a snag in the process. For example, as part of a healthcare organization, Passe's group needs to ensure that any data on returned tape is destroyed. That's often enough to deter a tape vendor from seeking the tape in question.

"They don't want to go through the hassle that it takes to certify that the data was destroyed on those tapes," says CareGroup's Passe. Quantum's Eastman says the company receives a "small percentage" of returned tapes that will go through a failure analysis process. Analyzing failures is a challenge, he adds, because you don't know how the cartridge was used and handled.

"We get the tapes back from the customer because we want to analyze the tape and understand why it failed in their environment," says Imation's Caprio. He adds that they'll provide a document saying they haven't read the data and certifying the destruction of the tape.

Figure 9

This was first published in February 2005

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