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When good tapes go bad
Generally, the number of tapes that failed on initial use was low--averaging less than one per month among all responses. Still, bad tapes out of the box were a bugaboo that haunted some respondents. "We recently had a bad batch of tapes that placed our entire enterprise tape backup at risk," noted one respondent who requested anonymity. "Going forward, tape will be used for long-term archive only, and backup will be to disk."
The causes of tape failures varied, but nearly 53% of respondents said media errors were sometimes, often or always the cause of their tape failures (see Figure 7, this page). Storage administrators admit that tape mishandling can often be the cause of a failure. "If a tape goes bad, I find it's usually a user error," said one candid respondent who indicated that dropping a tape is the most common user slipup. "It's very rare for LTO-1 or LTO-2 HP tapes to go bad on their own."
"I've had a lot of problems in the 9900 space with tape leaders being ripped off," says CareGroup's Passe. It was a disruptive enough matter that his group did a visual inspection of all 500 of their 9940 cartridges. They found about five cartridges that looked OK at first but had broken leaders. Passe hasn't run into this issue with 9840 tapes. "The 9840 tape technology is spoke-to-spoke with midmount heads so there's no leader--those definitely seem to be more reliable," he says.
Tape drives shared users' wrath aimed at tape media, with approximately 40% of respondents fingering these devices as sometimes, often or always the cause of their backup failures (see Figure 7, this page). "Tape drives are the most unreliable form of backup there is, with the exception of no backup," claimed one respondent.
The cost of failure
Taken individually, a tape cartridge is a modest expense--perhaps the cheapest item a storage manager will ever budget to buy. But as failed tapes pile up, the expense can become significant, if not considerable. Our survey finds that about half of respondents purchase fewer than 10 tapes per month, but more than a fifth (21.4%) buy more than 50 cartridges each month. At approximately $50 each, buying 50 tapes per month totals approximately $30,000 a year--a sum large enough to merit line-item status on most storage shop budgets.
Perhaps because the cumulative cost of failed tapes isn't apparent, 61% of respondents said they don't even bother trying to recoup the cost of cartridges gone awry. In some cases, this could mean writing off a fairly good chunk of change: 20.4% of respondents said failed tapes cost their organizations more than $300 a month (see Figure 8).
While the cost of failed tapes may not be an overriding issue, the potential for a failure to compromise data protection certainly is. Some respondents are resigned to the possibility of at least an occasional bad tape disrupting the backup process and take appropriate precautions. "Tape reliability can be a problem; but if you have a comprehensive, multitier backup plan in place, the potential for problems can be negligible," noted one respondent. Others are actively pursuing disk-based and even optical alternatives to reduce their reliance on tape for backup.
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