DLT or DAT tapes are best

Though 8mm and 4mm tape drives are slower than DLT drives, the high tape capacity makes them useful for unattended backups. 4mm DAT tapes can hold up to 2GB of raw data and 8mm can hold up to 5GB. The capacity of both can be pushed even higher with compression. DLT drives are very fast and can store large amount of data.

However, this does not mean that DLT/DAT tapes should always be used for unattended backups. Keep reading.