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Storage magazine's tape reliability survey was conducted in November 2004. Storage subscribers and SearchStorage.com members were contacted by e-mail and invited to participate. A total of 378 valid surveys were submitted.
If backup is painful for storage managers, then tape all too often inflicts that pain. Tape is the final destination of nearly all data--whether it's backed up for data protection or archive purposes--and has become the symbol of the backup process. Despite this, tape is considered the Rodney Dangerfield of storage media. It gets little respect for being part of a successful backup and restore, and more times than not it's blamed for a failure.

Storage surveyed its readers and SearchStorage.com members in November 2004 to determine how often unreliable tapes were at the heart of a backup snafu. When asked to describe the tape failure situation in their shops, nearly a third of the respondents (31.2%) said it was either a significant problem that often disrupts backups or a problem that sometimes disrupts backups.

Tape by its very nature is imprecise--it's essentially a ribbon of plastic that can stretch and shrink, and that's tugged across heads where it can slide up and down. "There's a lot of wear and tear," says Michael Passe, senior storage engineer at CareGroup Healthcare System/Beth Israel Deaconess Medical Center in Boston. "You're pulling this thin, long piece of iron oxide-coated plastic across a head about a couple of million times a year." And as opposed to sealed, fixed-placement disks, tapes are handled frequently and often transported.

Over the years, tape manufacturers have gone to extraordinary lengths to engineer products that can stand up to these harsh environments. New materials and built-in intelligence to monitor the health of the tape have made tapes more reliable. But it's a battle that's far from over. One respondent cited tape's "huge hidden management costs," while another added that "tape drives and media are the biggest problems in our shop."

Pinpointing tape-related problems can be tough. "Sometimes we're not quite sure whether we have a drive issue or a problem with the media," notes George Rogers, senior systems programmer for storage administration at CareFirst BlueCross BlueShield in Washington, D.C. Rogers says the error messages from his firm's backup applications give little indication if the media or the drive is the problem. And the problem may be compounded if a single bad tape affects multiple drives.

Despite all the horror stories, tape offers two compelling benefits: the lowest media price and portability. With ever-rising capacities and transfer rates, tape technology isn't sitting still. "For reliability, speed, ease of storage and dollar per gigabyte, nothing beats tape," commented one satisfied tape user.

Shouldering the backup burden
The 378 storage professionals who completed our survey come from a broad cross-section of industries, regions and storage shop sizes. On average, respondents' tape libraries were equipped with approximately 31 drives and more than 2,200 slots.

The amount of data respondents back up varied widely--a third back up more than 4TB per week (see Figure 1, this page), and nearly a fifth (18.8%) say they use more than 200 tapes a week (see Figure 2, this page).

The most popular tape format--by a wide margin--is DLT; more than 50% of respondents use this format (see Figure 3, this page). "DLT tapes have been extremely reliable," said one respondent, noting that his group has seen "only two or three media failures within the last 10 years." Hard on the heels of DLT are LTO-1 and LTO-2, which netted approximately 21% and 30% usage, respectively. Among the tape brands used most often by respondents were Fuji Photo Film U.S.A. Inc.(Fujifilm) (32.3%), Imation Corp. (28.6%) and Sony Electronics Inc. (24.1%). These brands were followed by a clutch of manufacturers garnering 17% to 19% of respondents' answers (see Figure 4).

Some users have experimented with different brands and found variations in tape quality. "Everybody's oxide is not the same," says CareFirst's Rogers. "Some break down quicker than others, and some of it doesn't adhere to the substrate as well as the others--there's definitely a difference in quality." But Rogers also found that trying different brands may not sit well with drive vendors; he ran into problems using media that his drive vendor said wasn't certified for its libraries. Even though CareFirst had used the brand before and was using it in other libraries from the same vendor, this didn't help to resolve the problem.

Figure 1

Figure 2

Figure 3

This was first published in February 2005

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