A tape drive can compress, or squeeze together, data you are backing up or archiving. Compressing data can double the amount of data you can store on a tape cartridge. Keep in mind that the amount of data actually compressed depends on the type of information you are storing. For example, a document will compress significantly more than a picture, video or sound file. Tape drives and cartridges indicate the compressed and uncompressed storage capacity.

When buying a tape drive, try to find a drive that can store all the files you want to back up or archive on a single tape cartridge to make it easier to store the information. DOS (Digital Data Storage) DDS drives are also known as DAT (Digital Audio Tape) drives. There are currently five types of DDS drives—DDS 1, DDS 2, DDS 3, DDS 4 and DDS 5. The larger the number that follows DDS, the more data the drive can store and the faster the transfer speed. DDS drives can store up to 36 GB (72 GB compressed) on a single tape cartridge. AlT (Advanced Intelligent Tape)

LTO (Linear Tape Open) There are currently two types of LTD drives—LTD 1 and LTD 2. The larger the number that follows LTO, the more data the drive can store and the faster the transfer speed. LTD drives can store up to 200 GB (400 GB compressed) on a single tape cartridge.

There are currently several types of AlT drives—AlT 1, AlT 2 and AlT 3. The larger the number that follows AlT, the more data the drive can store and the faster the transfer speed. AlT drives can store up to 100 GB (260 GB compressed) on a single tape cartridge.