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DAT
The DDS (Digital Data Storage) formats build on the 4 mm DAT (Digital Audio Tape) format to meet the more stringent needs of computer data storage. As the DDS technology has developed, so new standards have been produced, each allowing more data to be stored on a single cartridge. Briefly, the development of the DDS formats to date has been as follows:
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DDS-1 - DDS-1 was originally called DDS. It used 60m and 90m cartridges and did not allow hardware data compression.
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DDS1-DC DDS1-DC, or simply DDS-DC - extended DDS-1 to include hardware data compression. This typically doubled the capacity of a tape.
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DDS-2 - DDS-2 included the features of DDS-1 and DDS-DC, but increased the amount of data that could be written to a single cartridge in two ways:
Together these features meant that a DDS-2 tape could hold twice the data of a DDS-1 90m tape.
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DDS-3 - DDS-3 stores data at twice the density of DDS-1 and DDS-2, and also allows more of the tape to be used for data. As a result, a DDS-3 (125m) tape holds three times the data of a DDS-2 tape.
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DDS-4 - DDS-4 tape, at 150m, is longer than DDS-3 (125m) tape. It holds holds two-thirds more data than a DDS-3 tape.
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DAT-72 - DAT-72 tapes are 170m long and data is written in narrower tracks, again increasing data density, enabling tapes to hold 80% more data than DDS-4 tapes.
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DAT-160 - DAT-160 tapes are 154m long and data is written at a higher density than DAT-72, enabling the tapes to store up to 160GB of data.
- DAT-320 - DAT-320 tapes are 153m long and data is written at a higher density than DAT160, enabling the tapes to store up to 320 GB of data.
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To exploit the full potential of a DDS-format drive, matching cartridges should be used: DDS-3 cartridges for DDS-3 drives, DDS-4 cartridges for DDS-4 drives, and DAT 72 cartridges for DAT 72 drives.
This will allow the drives to store the maximum amount of data on a tape. However, HP DDS drives are backward compatible. This means that, for example, a DAT 72 drive can read and write DDS-4 tapes. Note that it will use DDS-4 format, so the full advantage of DAT 72 will be lost. Drives are not forward compatible, so, for example, a DDS-4 drive cannot read or write a DAT 72 tape. It will simply eject it.
The table below summarizes which drive can write and read which tapes.
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DDS-1 StorageWorks Media
(60m/90m)
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DDS-2 StorageWorks Media
(DAT-8)
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DDS-3 StorageWorks Media
(DAT-24)
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DDS-4 StorageWorks Media
(DAT-40)
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DAT 72 StorageWorks Media
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DAT 160 StorageWorks Media
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DAT 320 StorageWorks Media
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HP Surestore 2000/5000
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Write/Read
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No
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No
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No
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No
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No
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No
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HP Surestore/StorageWorks
DAT 8
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Write/Read
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Write/Read
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No
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No
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No
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No
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No
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HP Surestore/StorageWorks
DAT 24/24x6
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Write/Read
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Write/Read
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Write/Read
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No
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No
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No
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No
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HP StorageWorks DAT40 Hotplug
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No
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Read Only
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Write/Read
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Write/Read
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No
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No
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No
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HP Surestore/StorageWorks
DAT 40/40x6
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No
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Write/Read
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Write/Read
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Write/Read
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No
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No
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No
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HP StorageWorks DAT 24 USB
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No
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Write/Read
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Write/Read
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No
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No
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No
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No
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HP StorageWorks DAT 40 USB
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No
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Write/Read
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Write/Read
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Write/Read
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No
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No
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No
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HP StorageWorks DAT 72 USB
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No
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No
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Write/Read
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Write/Read
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Write/Read
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No
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No
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HP StorageWorks DAT-72 / 72x6
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No
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No
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Write/Read
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Write/Read
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Write/Read
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No
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No
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HP StorageWorks DAT 160 SCSI Tape Drive
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No
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No
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No
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Write/Read
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Write/Read
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Write/Read
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No
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HP StorageWorks DAT 160 USB Tape Drive
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No
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No
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No
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Write/Read
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Write/Read
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Write/Read
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No
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HP StorageWorks DAT 320 SAS
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No
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No
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No
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No
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No
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Write/Read
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Write/Read
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HP StorageWorks DAT 320 USB
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No
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No
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No
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No
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No
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Write/Read
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Write/Read
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Please be aware that media compatibility for the HP StorageWorks DAT40 Hotplug drive is different to the media compatibility for other HP Surestore DAT40 drives.
The table below displays a matrix of difference in media compatibility.
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DDS-1 Media
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DDS-2 Media
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DDS-3 Media
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DDS-4 Media
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DAT-72 Media
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DAT-160 Media
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HP StorageWorks DAT40 Hotplug drive
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No
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Read only
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Read/Write
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Read/Write
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No
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No
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HP Surestore DAT40 drive
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No
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Read/Write
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Read/Write
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Read/Write
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No
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No
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To identify computer-grade DDS media easily, look for the DDS logos. These indicate that the media meets the DDS specifications laid down by the ECMA, ISO/IEC and ANSI standards. Logos for the various generations of DDS tape are shown in the table below.
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Logo
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Description
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DDS/DDS-1 logo
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DDS-1 MRS logo
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DDS-2 logo
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DDS-3 logo
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DDS-4 logo
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DAT-72 logo
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DAT-160 logo
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DAT-320 logo
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The Media Recognition System (MRS) enables drives to identify DDS-grade media. DDS MRS cartridges have a series of stripes on the transparent leader at the beginning of the tape. HP drives can be configured to treat non-MRS tapes as write-protected. In other words, the drive will only be allowed to read non-MRS cartridges, not write to them. DDS-1 MRS tapes can be recognized by the logo shown in the illustration above. MRS is used on all DDS-2, DDS-3, DDS-4 and DAT 72 tapes with the logos shown above.
Cartridges with the old DDS/DDS-1 logo are in no way inferior; they simply do not carry the stripes on the leader tape, so the drive cannot recognize them as DDS. All DDS-1 cartridges produced from early 1993 should have the Media Recognition System stripes.
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