When looking for a backup solution for your computer system, tape systems are still a strong contender when compared with newer technologies. Tape has the lowest cost per megabyte. Since they are removable media, the backup can be stored offsite in case of disaster. Tapes allow easy expandability, since backups can be spanned across multiple cartridges.
Once you decide on tape as your backup medium of choice, there are still several other decisions to be made.
- Internal or external: An internal tape drive requires no additional desktop space as long as there is room in the computer chassis. An external drive connects to the computer with a cable and can be moved from machine to machine to allow a single tape device to back up several systems.
- Interface: The interface is the way the tape drive connects to the computer. Most tape drives use a SCSI interface, but others connect with Fibre Channel, USB, or the parallel port.
- Capacity: Optimally, you want a tape backup system that can store your entire backup on a single cartridge so you can run the backup unattended. Capacities are reported as two numbers, for example 20 GB/40 GB. The first is the uncompressed capacity of the tape. Since tape backups automatically compress the data, more than 20 GB will actually be stored on this tape. Most manufacturers estimate compression at 2:1, so it is likely you can store 40 GB of data on this 20 GB tape. Capacities listed below are all uncompressed capacities.
- Speed: Measured in MB/s, speed lets you estimate how long the backup will take. If you have a large backup or a limited window of backup time, you may want to find a fast solution.
- Cartridge Life: Tapes are a mechanical system and cartridges eventually fail. There are two considerations for cartridge life. Shelf life is how long the cartridge will last in storage. This is an important consideration if you are making archive backups, backups that are recorded then saved for many years. Usage life is measured in passes, which is how many times the tape is wound completely from one end to another. This is a more useful measure for typical backup use, where older backup tapes are re-used for new backups.
With these factors in mind, you need to consider which technology serves your needs. The most common tape technologies are listed below. They all have shelf lives of 30 years except for DDS, which has around half the life. These technologies have gone through multiple revisions and only the latest revision is shown.
- DDS (Digital Data Storage)
- Capacity: 36 GB
- Speed: 3 MB/s
- Usage Life: 2,000 passes
- AIT (Advanced Intelligent Tape)
- Capacity: 100 GB
- Speed: 12 MB/s
- Usage Life: 30,000 passes
- DLT (Digital Linear Tape)
- Capacity: 40 GB
- Speed: 6 MB/s
- Usage Life: 1,000,000 passes
- LTO (Linear Tape Open) - ULTRIM
- Capacity: 200 GB
- Speed: 30 MB/s
- Usage Life: 1,000,000 passes
DDS is a good, inexpensive choice for the average home user while the other technologies are more appropriate to a large office environment. A tape system used with a well thought out backup plan and, if possible, offsite tape storage, will protect your important data against disasters from a computer virus to a fire.