IT Management

Tape: A Collapsing Star

5 Pages

The Library of Congress and the National Media Lab recommend:

  • Keeping storage areas at a constant 45 to 50° F or colder
  • Not storing magnetic tapes below 46° F (because it may cause lubrication separation from the tape binder) and 20 to 30 percent Relative Humidity (RH) for magnetic tapes (open reel and cassette); 45 to 50 percent RH for all others
  • Ensuring environmental conditions don’t fluctuate more that ±5° F or ±5 percent RH over a 24-hour period
  • Storing in dark areas except when being accessed
  • Keeping recordings away from UV sources (unshielded fluorescent tubes and sunlight). 

Widely fluctuating temperature or RH severely shortens the life span of all tape. This is one of the main reasons tape is viable only for the large enterprise that can afford a library large enough to maintain tape on a raised floor with handling by a robot.

There are many other considerations. The design of the cartridge and the transport are critical to tape reliability. Only recently have tape transports become reasonably reliable. The enterprise class transports today are in the 400,000-hour range, with a well-managed cartridge (meaning temperature and humidity controlled environment) having a stagnant cartridge (meaning it’s not being used—which would otherwise shorten its life) with a shelf life of 15 to 30 years.

When data is stored on a cartridge, it must be in a temperature and humidity controlled environment. The cartridge also shouldn’t be handled if you want to maintain the integrity of the data. As the cartridge is sitting in a slot, after 10 years, three generations of transports have been introduced into the market. Considering the whole shelf life of about 20 years, at least six generations of change would have evolved in transports. Unless you kept the transport you wrote the cartridge with, system software, operating system, computer hardware, operations manuals, and ample spare parts, along with the recorded media, you can’t get your data. Even with all those things and in perfect environmental conditions, your chances of getting data back are about 27 percent. Does that realistically protect your business and mitigate legal risk?

By the way, if anything at all went wrong with that tape, or the other 30 cartridges that were used for a backup, there’s no redundancy and you can’t get your data. IT organizations deal with this by re-mastering data onto new transports and new media with every generation they change. Changing out media and re-mastering is expensive.

The mechanism for reading and writing tape is much more complicated than disk, where you have a nice flat stable surface that spins without flexing in a hermetically sealed and contaminate-free enclosure. By contrast, take a spool of paper out in the wind and unwind it in the breeze. The problem with a tape transport is trying to keep that surface flat and tracking to be able to read anything that was written. It’s difficult, and many factors can make it all stop working. Again, disk is simple by comparison, which is why the reliability numbers of disk are in the 1.2 million hour range vs. less than half that for the best tape transport. If you’re using Digital Linear Tape (DLT), the life is more like 250,000 hours for the transport, and the shelf life of the media is more like 10 years in perfect conditions.

Disk Availability

Disk, unlike tape, has a multitude of reliability and protection elements, such as Redundant Array of Inexpensive Disk (RAID), that are built in and commonly used. Because tape lacks RAID-type capabilities, when one tape out of a backup job group fails, the integrity of the whole restore collapses when multi-threading is used.

Disk has long been trusted as highly available. Disk used as a protection library is no exception. Whether you need a remote office, small office, entry-level system, or enterprise class with petabytes of capacity, disk products are redundant, protected and highly available, serving the need to recover and meet regulatory requirements.

RAID 6 is ultra reliable, protecting you from double drive failures, and providing an extra level of protection for your recovery data, a wise choice when using disk as a protection library.

Conclusion 

With more than 70 percent of users using disk backup today, disk is a wise choice. It’s more affordable than tape when you consider labor and downtime costs. The ability to rapidly back up and recover is paramount for business continuity planning. Backing up to disk is fast; recovery is faster. The use of a Massive Array of Idle Disk (MAID) approach also can save a great deal of energy. You can reduce your comparable energy costs for power and cooling by as much as 60 percent. Finally, you can reduce the total amount of space required to maintain your backup archive when you use de-duplication.

Using disk as a protection library will make the people you have more efficient, enabling them to do more, while you pay less. Using disk as a protection library will help you get your business back up fast.

5 Pages