Tape backup is a form of data backup using magnetic tape as the medium for storage instead of hard disks. Tape backup drives are used to periodically copy data from a primary or secondary storage device for archiving or disaster recovery. This form of backup can be done manually or using a software that can handle backup procedures automatically.
Data stored on tape must be accessed sequentially unlike a disk drive, which provides random access to data elements. This is one of the disadvantages of tape because it can take more time to wind the tape reels to the piece of data you want. It also takes a longer time to write large amounts of data. However, tape is especially well suited for sequential data streaming. Modern LTO tape drives can match the continuous transfer rates of most 10k RPM hard disks at 80MB/s. Linear Tape-Open (LTO) technology is an open tape standard from HP, IBM, and Seagate that is widely used throughout the IT industry.
While tape is good for long term data integrity during storage, the data can easily be damaged by magnetic waves, but the same is true for magnetic hard disks. Another disadvantage of tape is an effect called shoe-shining that can occur during read/write operations when the data transfer rate slows down past a certain point. When this happens, the streaming must be stopped and the tape must be rewound to that point. This back and forth motion causes the tape to degrade. This effect has been minimized in modern tape systems with variable speeds, but it still happens if the computer streams data at a rate that is consistently below the lowest speed level.
Although tape storage is older technology that is being used less and less, there are still plenty of existing tape backup devices for personal computers and for large enterprises as part of storage area networks (SANs). Tape still maintains several advantages such as low unit cost and long term data storage integrity. Tape storage can support hundreds of gigabytes of storage, and they usually have a data compression ratio of two to one. The tape drive will list the true storage capacity and the compressed capacity. The low cost is the main reason why tape backup is still used in very large enterprises that have a huge amount of data to backup. Tape storage can also be easily moved off site.
Sep 15 '10 at 02:33 PM