For many years tape media was the only choice for backup due to its cost advantage. The chart below shows the recent trends in tape media prices vs hard disk media prices. As you can see, as long ago as 2002, hard disks caught up with tape media and now the debate between the two media types is more complex.
This article is not intended to be conclude whether one type of media is better than the other. Indeed the sands are continually shifting with new and better tape drives released and smaller and higher capacity hard drives arriving almost weekly. Also, the answer to the question depends on the application and type of organisation. Instead this article provide a short framework of criteria that a Network Administrator should consider when making the decision.
Advantages of Tape
Advantages of Disk
|Portability||More compact and lighter wieght than hard disk.|
|Reliability||Low MTBF (mean time between failure). Hard disk is invariably significantly more reliable than tape. The only exception to this is that tape can in some instances have better resistance to shock.|
|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 whilst it can take minutes to seek the the correct place on a tape.|
|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.|
|Price||As shown in the graph, hard disks seems to be cheaper than equivalent tape media. However this trend may not continue if new tape products are launched.|
|Speed||Raw data transfer rates tend to be superior, although the interface via which the device is connected can tend to limit the transfer rate. With the advent of 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.|
To be continued