Digital Data Storage (DDS)
Digital Data Storage (DDS) evolved from the Sony's Digital Audio Tape (DAT) technology.
In 1989, Sony and Hewlett-Packard defined the DDS format for data storage using DAT tape cartridges.
DDS uses a 4mm tape and the drive uses helical scanning for recording; the same process used by a VCR.
There are two read heads and two write heads. The read heads verify the data as it is written, and naturally if errors are present, the write heads rewrite the data.
There are four types of DDS drives:
- DDS-1: Stores up to 2GB of uncompressed data on a 120-minute cartridge.
- DDS-2: Stores up to 8GB of data in compressed format on a 120-minute cartridge.
- DDS-3: Stores up to 24GB of data on a 125-minute cartridge. DDS-3 uses PRML (Partial Response Maximum Likelihood), which eliminates electronic "noise" for a cleaner data recording.
- DDS-4: The newest DDS format, DDS-4 stores up to 40GB of data on a 125-minute cartridge.
It is important to note that a DDS cartridge needs to be retired after 2000 passes or 100 full backups.
You should clean your DDS tape drive every 24 hours of operation with a cleaning cartridge and discard the cleaning cartridge after 30 cleanings. DDS tapes have an expected life of at least 10 years.
