Tape Backups

Tape, in contrast to disk, is physically delicate and easily compromised by environmental factors such as heat, humidity, and magnetic interference. Moreover, tape cartridges must be replaced frequently (every 6-12 months). Tape’s innate sensitivity contributes to high failure rates, with analysts estimating that anywhere from 42 to 71 percent of tape restores fail.

Even when magnetic tape backups are successful, tapes themselves are subject to loss or theft, and may be in the possession of an employee or vendor unable to reach a recovery site. Thus, even when physical backup and restoration processes succeed, tape may not prove to be as timely and appropriate a medium for data storage as disk. Time is a crucial consideration because each hour of server, application, and network downtime endured until data restoration comes at a high cost, especially to smaller businesses.

With disk storage the answer is, pretty quick. Unlike tape, which typically stores data in a linear fashion, meaning you have to start at the beginning and run through it until you find what you're looking for. Disk storage is more like a mirror, reflecting every aspect of your system at once. 

All a tape does is store data, whereas the best disk-based software can take a complete image of your OS, your settings and your applications. With a disk solution, you don't have to search for media; you don't have to search for applications. It is all right there.

Advantages of Tape

Portability
More compact and lighter weight than hard disk.

Advantages of Disk

Reliability
Low MTBF (mean time between failure). Hard disk is invariably significantly more reliable than tape, virtually 100% versus over 40% failure rate for tape backups. The only exception to this is that tape can in some instances have better resistance to shock.

Ease and speed of recovery
Recovery time from a server crash is 2 hours or less versus 16-40 hours for tape.

Price 
As shown in the graph to the right, hard disks are now cheaper than equivalent tape media.

Long Life
Whilst each tape is specified to have only a limited number of read/write cycles, hard disks have virtually no limitation in this regard.

Random Access
No winding or seeking to find information. Within backup applications this contributes to much faster backup and restore times. Hard disk access times are typically 10 milliseconds while it can take minutes to find the correct place on a tape.

Speed 
Superior raw data transfer rates, although the interface via which the device is connected can limit the transfer rate. With USB2 and SATA, the raw speed advantage of hard disk is confirmed.

Rewritabilty
Instant ability to write over data, whereas tapes can require erase cycles and re-tensioning.