HP LTO 4 SCSI, LTO 4 FC, LTO 4 SAS manual How WORM media works, Changes to SCSI commands

The following table gives the minimum acceptable Capacity Proportion Values and the approximate capacity they will give:

Cartridge	Min. capacity proportion value	Resultant approx. min. capacity	Max. capacity
Ultrium 2	1605h	17.2 GB	200 GB
Ultrium 3	151Ah	33 GB	400 GB
Ultrium 4	1055h	51 GB	800 GB

NOTE: Capacities are approximate and can be affected by defects that reduce the actual capacity of the tape. Other factors, such as compression and block packing, may also affect capacity.

WORM media

HP Ultrium-3 WORM (Write Once—Read Many) data cartridges are two-tone grey/yellow to distinguish them from RW media. They have a unique Cartridge Type stored in the Cartridge Memory, so that they will be rejected by non-WORM compatible drives. For automation configurations with auto-eject disabled, the cartridge will not be physically ejected from the drive but held at the “ready eject” position.

The write-protection tab behaves as on Read/Write (RW) cartridges.

How WORM media works

Drives use the EOPD (End of Protected Data) value to control the use of WORM tapes.

EOPD is a logical position on tape that is automatically calculated based on the End of Data (EOD) value read from the Cartridge Memory (CM) when the cartridge is loaded into the drive. The EOD value is an “intrinsic” code stored and protected in the Cartridge Memory of each WORM cartridge, and updated after each write session. The EOPD indicates that data between BOM and this position cannot be overwritten.

The EOPD value is held within the drive’s memory. It is updated automatically and continuously as each block of data (typically 64 or 128 KB) is written to tape, so the EOPD value indicates a logical position immediately after the last block of data written to tape.

When the cartridge is unloaded, the drive updates the EOD value in CM to reflect the end of successfully written data on the cartridge, and clears the EOPD value stored within the drive. Any future writes to the cartridge will occur after the location of the EOD, which will become the initial location for EOPD during the next write operation.

Changes to SCSI commands

New additional sense codes and TapeAlert flags

ASC/Qs:

•300Ch (WORM medium—overwrite attempted)

•300Dh (WORM Medium—integrity check failed)

22 Use of tapes

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