The mere mention of tape backup evokes a cacophony of rolling eyes and deep sighs from all within earshot. Everyone hates tape. System administrators hate it. Managers hate it. Data center administrators hate it. Even the random person on the street, if asked his opinion of tape, probably hates it. Everyone hates tape. But tape works. It has its advantages and its disadvantages. Unfortunately, for the foreseeable future, tape's advantages outweigh its disadvantages. Tape, we admit half-heartedly, is here to stay. If you're puzzled over this hate-hate relationship with tape, these 10 reasons will enlighten you as to why tape will reside in our data centers for a while longer.
Of course, it's cost. It always boils down to cost, doesn't it? Cost is the primary reason for using tape. It's cheap to buy, cheap to maintain, and cheap to store. No other media comes close to the price of tape. This reason alone will keep tape in your data center for a few more years.
Just behind cost is portability. Tape is highly portable. Tape is a removable media. It is light to carry, it takes up little space, and it travels well. What more could you ask for from an inexpensive media?
3. Shelf Life
Tape has a long shelf life. The reasons for its long shelf life are that the media itself is durable: Plastic. It's flexible, it's resistant to moisture and mildew and it's temperature-stable. Tape has a standard shelf life of more than 30 years with some manufacturers boasting of shelf life exceeding 50 years. Unlike other media, tape is time-proven since its widespread adoption in the 1950s. Tape is here to stay because tape is built to be here to stay.
Although everyone complains about tape reliability, it is a very reliable media. Rarely does the media itself fail. You can usually trace the problems surrounding tape's bad reputation back to incidences of human error and not tape error. Tape, when used correctly, is reusable and reliable, rivaling all other media types for reliability.
Tape is a convenient medium. If you use virtual tape libraries (VTLs), you still use tape to offload your data for archival storage. VTLs are fast because they're disk-based, but they lack the portability of tape. Tape is convenient because it's used to offload data without clogging production networks or slowing disks to a crawl to make those snapshots. Disk-to-disk backups still rely on the convenience of tape.
6. Media Size
Tape has an almost unlimited media size because of the ability to span huge backups across multiple tapes. The other buzzworthy term for this phenomenon is "scalability." Tape has an almost infinitely scalable design. You can backup an entire data center with tape. Then you can do it again tomorrow, the next day and so on.
Tape is a reliable media, even under extreme conditions. If a tape cassette fails, you can salvage the data by winding the tape onto an empty cassette. Tape drives are extremely reliable and able to operate with thousands of hours between failures. Most failures are mechanical problems with the drive mechanisms and not with the media. Tape drive reliability (250,000+ hours MTBF) is difficult, if not impossible, to replicate with spinning disks because storage media and the mechanical drive are separate entities. Your tape drive might fail, but chances are slim your data will go with it. Data that resides on disks, however, is not so lucky.
8. Power Consumption
Tape drive power consumption is very low on a per-gigabyte (GB) or per-terabyte (TB) level. The average power consumption for a Quantum LTO04HH Model B drive is 20 Watts. The new 'green' disk drives consume approximately 5 Watts each. It doesn't take a mathematical genius to realize how much required power you'll need to build an equivalent tape replacement system with disks.
Tape drives perform at very high speeds (for tape) in the range of 30 to 80MB/sec sustained and bursts to 300+MB/sec. At these speeds, offloading data to tape still makes sense for the largest enterprises. No, tape doesn't break any speed records, but for offloading from VTLs, speed is not a major concern.
Backup automation is a huge advantage of tape backup for enterprises. Using autoloaders, tape backup systems can run continuously, which means backups may run with minimal human intervention. Automated media exchange is a labor saver that keeps backup operations running smoothly.
Ken Hess is a freelance writer who writes on a variety of open source topics including Linux, databases, and virtualization. He is also the coauthor of Practical Virtualization Solutions, which was published in October 2009. You may reach him through his web site at http://www.kenhess.com.