HP LTO 4 FC Using CM to check tape integrity, Behavior with a missing or inconsistent EOD value

application to locate the tape in preparation for subsequent writing or reading operations. At the start of an appending archive or backup session, it is common for the application to locate the tape to a logical position immediately preceding the second filemark and to overwrite the second filemark during the data appending session.

Writes are allowed:

•when the current logical position is at EOD. This means that the drive must have read the EOD from tape before attempting to overwrite it.

•when there are only filemarks between the current logical position and EOD, and at least one filemark immediately before the current logical position.

Using CM to check tape integrity

Drives that support WORM cartridges check that the anti-tampering measures have not been violated before and during media access operations. If a violation is detected, for example, if the content of the CM does not match the content of the tape, the cartridge is treated as read-only, and Tape Alert flag 3Bh (WORM medium—integrity check failed) is set.

HP strongly recommends that software applications check for the presence of TapeAlert flag 3Bh after a tape load and periodically during operation. If the flag is set, the software should alert the operator and log the incident for audit.

Hosts can use the WTRE bit on the Device Configuration mode page (bit 6, byte 15 of mode page 10h) to control the behavior of the drive when reading WORM media whose WORM integrity is in doubt and which may have been tampered with. See details of the mode page in Chapter 4 in SCSI Interface, volume 4 of the HP LTO Ultrium Technical Reference Manual for more information.

Behavior with a missing or inconsistent EOD value

A missing EOD value or one in which the value on tape differs from that in CM can be caused by:

•CM corruption

•deliberate, malicious alteration of the EOD value in the CM

•an interruption of the drive power supply while writing data.

If the CM indicates that the EOD is not valid (for example, if the drive has powered down during a write), TapeAlert flag 04h (Media) will be set on cartridge load.

The drive behaves as for a RW cartridge with no EOD data set, except that any attempt to overwrite data will be rejected with CHECK CONDITION, a sense key of Data Protect and additional sense of 2700h (write-protected). Tape Alert flag 09h (Write-Protect) is set.

Unique media identifier

For added security, HP strongly recommends that applications read and track cartridge manufacturer and serial number values from the Cartridge Memory using MAM access commands:

•Attribute ID 0x0400: Cartridge manufacturer ID

•Attribute ID 0x0401: Cartridge serial number

Both values should be read and concatenated to ensure that the number is unique.

24 Use of tapes

HP restricted