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DAT

DAT
DDS1
DDS2
DDS3
DDS4
DDS5
DDS6
DDS7

Overview

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:
  • DDS-1 - DDS-1 was originally called DDS. It used 60m and 90m cartridges and did not allow hardware data compression.

  • DDS1-DC DDS1-DC, or simply DDS-DC - extended DDS-1 to include hardware data compression. This typically doubled the capacity of a tape.

  • 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:

    • It used longer, thinner tapes (120m).

    • It wrote data in narrower tracks.

    Together these features meant that a DDS-2 tape could hold twice the data of a DDS-1 90m tape.

  • 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.

  • 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.

  • 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.

  • 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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HP Surestore/Storageworks DAT Media Compatibility

Choosing Cartridges

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.

Read/Write Compatibility Table

The table below summarizes which drive can write and read which tapes.

DDS-1 StorageWorks Media
(60m/90m)
DDS-2 StorageWorks Media
(DAT-8)
DDS-3 StorageWorks Media
(DAT-24)
DDS-4 StorageWorks Media
(DAT-40)
DAT 72 StorageWorks Media
DAT 160 StorageWorks Media
DAT 320 StorageWorks Media
HP Surestore 2000/5000
Write/Read
No
No
No
No
No
No
HP Surestore/StorageWorks
DAT 8
Write/Read
Write/Read
No
No
No
No
No
HP Surestore/StorageWorks
DAT 24/24x6
Write/Read
Write/Read
Write/Read
No
No
No
No
HP StorageWorks DAT40 Hotplug
No
Read Only
Write/Read
Write/Read
No
No
No
HP Surestore/StorageWorks
DAT 40/40x6
No
Write/Read
Write/Read
Write/Read
No
No
No
HP StorageWorks DAT 24 USB
No
Write/Read
Write/Read
No
No
No
No
HP StorageWorks DAT 40 USB
No
Write/Read
Write/Read
Write/Read
No
No
No
HP StorageWorks DAT 72 USB
No
No
Write/Read
Write/Read
Write/Read
No
No
HP StorageWorks DAT-72 / 72x6
No
No
Write/Read
Write/Read
Write/Read
No
No
HP StorageWorks DAT 160 SCSI Tape Drive
No
No
No
Write/Read
Write/Read
Write/Read
No
HP StorageWorks DAT 160 USB Tape Drive
No
No
No
Write/Read
Write/Read
Write/Read
No
HP StorageWorks DAT 320 SAS
No
No
No
No
No
Write/Read
Write/Read
HP StorageWorks DAT 320 USB
No
No
No
No
No
Write/Read
Write/Read

HP StorageWorks DAT40 Hotplug Drive (Q1546A)

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.

DDS-1 Media
DDS-2 Media
DDS-3 Media
DDS-4 Media
DAT-72 Media
DAT-160 Media
HP StorageWorks DAT40 Hotplug drive
No
Read only
Read/Write
Read/Write
No
No
HP Surestore DAT40 drive
No
Read/Write
Read/Write
Read/Write
No
No

Media Recognition System

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.