Why the tape media is mostly used for back up purposes?

Tape drives are a form of digital storage devices which use tape for information recording. Because of the cost effective nature of the tape material and their long archival life, tape drives are widely used for backup and archival purposes. A tape drive cannot be accessed randomly like with the hard drives to read a particular piece of data. However, the tape drives can stream data very fast once they are positioned to the particular data point. Because of this factor, tape drives cannot be used for daily storage purposes. There are many formats available for storage of digital information on tape drives. Some of the popular ones are DDS (Digital Data Storage), AIT (Advanced intelligent tape) introduced by Sony and many others. These formats have several generations. AIT is a high speed format for data storage on tapes.
The raw data capacity of tape drives is fixed. However, more amounts of data can be stored on them by using compression. Most of the tape drives have a compression ratio of 2:1. Some tape drives when used with only certain data types can achieve a compression of about 10:1 also. Tape drives can be connected to the computer by using a SCSI interface or other common types as firewire and usb. The reliability according to the recently conducted surveys is not good. Most companies do not test or try to recover from tape archives and some companies that do experienced 77 % failure in achieving a backup of stored data. So, many of the companies in 2011 are starting to move from a tape based back-up solution to a disk based solution.
A large collection of tapes in a huge structure with a mechanical tape loading device is called a tape library. Tape libraries are used for heavy data archival needs like that of financial records of a company. These data facilities take up a lot of money to setup and maintain. A tape library is a digital archive that can store huge amounts of data ranging from several TB to few PetaByte or few 1000 TBs. A trade off exists for higher storage capacities. The access time becomes slower because of mechanical parts and machines when the storage amount increases. Tape autoloaders are tape library devices with a single drive. There are several software technologies for operation of tape libraries. Some of them include open source tape library softwares like AMANDA, Bacula, and the minimal mtx program.

By: Sandeep Mahanthi