The many complications and risks of tape

Magnetic tape technology was adopted for backup many years ago because it met most of the physical storage requirements, primarily by being portable so that it could be transported to an off-site facility. This gave rise to a sizeable ecosystem of related backup technologies and services, including tape media, tape drives, autoloaders, large scale libraries, device and subsystem firmware, peripheral interfaces, protocols, cables, backup software with numerous agents and options, off-site storage service providers, courier services, and a wide variety of consulting practices to help companies of all sizes understand how to implement and use it all effectively.

Tape media
Tape complexity starts with its physical construction. In one respect, it is almost miraculous that tape engineers have been able to design and manufacture media that meets so many challenging and conflicting requirements. Magnetic tape is a long ribbon of multiple laminated layers, including a microscopically jagged layer of extremely small metallic particles that record the data and a super-smooth base layer of polyester-like material that gives the media its strength and flexibility. It must be able to tolerate being wound and unwound and pulled and positioned through a high-tension alignment mechanism without losing the integrity of its dimensions. Manufacturing data grade magnetic tapes involves sophisticated chemistry, magnetics, materials, and processes.

Unfortunately, there are many environmental threats to tape, mostly because metals tend to oxidize and break apart. Tape manufacturers are moving to increase the environmental range that their products can withstand, but historically, they have recommended storing them in a fairly narrow humidity and temperature range. There is no question that the IT teams with the most success using tape take care to restrict its exposure to increased temperatures and humidity. Also, as the density of tape increases, vibration during transport has become a factor, resulting in new packaging and handling requirements. Given that tapes are stored in warehouses prior to being purchased and that they are regularly transported by courier services and stored off-site, there are environmental variables beyond the IT team’s control—and that makes people suspicious of its reliability.

Tape’s metallic layer is abrasive to tape recording heads and constantly causes wear and tear to them. Over time the heads wear out, sometimes much faster than expected. It can be very difficult to determine if the problem is head wear, tape defects, or dirty tape heads. Sometimes the only remedy is to replace both the tape heads and all the tapes. The time, effort, and cost involved in managing
wear-and-tear issues can be a sizeable burden on the IT group with no possible return on that investment to the organization. Tape aficionados are very careful about the tapes they buy and how they care for them, but many IT leaders no longer think it is worthwhile to maintain tapes and tape equipment.

Media management and rotation
Transporting tapes also exposes them to the risk of being lost, misplaced, or stolen. The exposure
to the organization from lost tapes can be extremely negative, especially if they contain customer account information, financial data, or logon credentials. Businesses that have lost tapes in-transit have not only had to pay for extensive customer notification and education programs, but they have also suffered the loss of reputation.

Backup software determines the order that tapes are used, as well as the generation of tape names. Unfortunately, tapes are sometimes mislabeled which can lead to incomplete backup coverage, as well as making restores and recoveries more challenging. It sounds like a simpleproblem to solve, but when you consider that multiple tapes may have been used as part of a single backup job and that some tapes (or copies of tapes) are off site and cannot be physically checked, it turns out that there is not always a fast way to clear up any confusion.

Tape rotation is the schedule that is used by backup software to determine which tapes should be used for the next backup operation. If an administrator improperly loads the wrong tape in a tape drive, the backup software may not run, which means new data is not protected.

Conversely, the backup software may choose to overwrite existing data on the tape, making it impossible to recover any of it. A similar problem occurs when a backup administrator erroneously deletes tape records from the backup system’s database or erases the wrong tapes. Backup only works correctly when the database used to track data on tape accurately reflects the data that is recorded on tapes.

These sorts of problems are well-known to backup administrators and are more common that one might think. Backup administration and tape management tends to be repetitive, uninteresting work which sets the stage for operator oversights and errors. This is the reality of tape backup and it is why automated data protection with the Microsoft HCS solution from

Microsoft is such an important breakthrough. It removes the responsibility for error- prone processes from people who would rather be doing something else. When you look at all the problems with tape, it is highly questionable as an infrastructure technology. Infrastructures should be dependable above all else and yet, that is the consistent weakness of tape technology in nearly all its facets.

Synthetic full backups
An alternative to making full backup copies is to make what are called synthetic full copies, which aggregate data from multiple tapes or disk-based backups onto a tape (or tapes) that contains all the data that would be captured if a full backup were to be run. They reduce the time needed to complete backup processing, but they still consume administrative resources and suffer from the same gremlins that haunt all tape processes.

The real issue is why it should be necessary to make so many copies of data that have already been made so many times before. Considering the incredible advances in computing technology over the years, it seems absurd that more intelligence could not be applied to data protection, and it highlights the fundamental weakness of tape as a portable media for off-site storage.

Restoring from tape
It would almost be comical if it weren’t so vexing, but exceptions are normal where recovering from tape is concerned. Things often go wrong with backup that keeps it from completing as expected. It’s never a problem until it’s time to recover data and then it can suddenly become extremely important in an unpleasant sort of way. Data that was skipped during backup cannot be recovered. Even worse, tape failures during recovery prevents data from being restored.

Unpleasant surprises tend to be just the beginning of a long detour where restores are concerned. Fortunately, there may be copies from earlier backup jobs that are available to recover. Unfortunately, several weeks or months of data could be lost. When this happens, somebody has a lot of reconstruction work to do to recreate the data that couldn’t be restored.

One thing to expect from disaster recovery is that more tapes will need to be used than assumed. Another is that two different administrators are likely to vary the process enough so that the tapes they use are different—as well as the time they spend before deciding the job is done, which implies the job is never completely finished. Most people who have conducted a disaster recovery would say there was unfinished business that they didn’t have time to figure out. Their efforts were good enough—they passed the test—but unknown problems were still lurking.

Source of Information : Rethinking Enterprise Storage

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