Tapes are the earliest forms of data backup. A tape media consists of a long flexible ribbon made of flexible plastic coated with magnetic media. The tape is wound on spindles and stored in mechanical cartridges that protect it from dust.
 
Backups made to tape media are mostly used in corporate environments due the following reasons:

• They are very costly
• Tape media are able to store huge amounts of data
• These have a long life

Tapes are usually able to hold data in the range of hundreds of gigabytes. For example, the Sony Advanced Intelligent Tape 5 (AIT) tape format has capacity of 400 GB while delivering backward compatibility with AIT 3 & 4. Further sustained native transfer rate occurs at a rate of 24 Mbps. Also, the backups can be made in compressed form. With a compression ratio of 2.6:1, you can store one terabyte (1024 GB) of data on a single tape. This is a huge amount of data. Typical home users will rarely need to use tape backups unless they have hours and hours of high quality video files to archive.
 
Backups to tape media have an average life span of 30 years. The only condition is that they need to be stored at a particular temperature (usually 20º C) and humidity (usually 40% non-condensing humidity)
 
Nowadays, backup to external drives have also emerged as a solution to huge amount of data storage. External drives differ from tape storage by providing random access to the data stored. Also, in the case of data restoration, data is quickly available directly from the external hard disk whereas you need to restore data to a hard disk from tape media before it can be used. External drives do not require delicate handling as compared to tape media. They can tolerate a wide margin in the temperature and humidity.
 
Another difference between tape storage and external drives is the fact that tape media backup is not supported for notebook computers. So, external drives are more suited to back up for portable computers. Moreover, external hard drives do not take any special software to access the data stored on them. Hence even if the computers would have evolved in the years between when the backup was taken and when the data needs to be restored, external hard disks will be usable. But it may happen that the tape drive is not readable by the newer computers.
 
Ultimately, whether you choose tape media or external drives is an individual choice based upon the requirements of the organization or personal computer. The important thing is that you follow a regular backup plan and periodically verify that the backup media is able to restore our data as and when required.