Oracle ZFS Storage Appliance: NDMP Backup Server Encounters Tape IO Error During LTO-5 Tape Drive Initial Access, Places Drive in "Append Only Mode" (Doc ID 1368914.1)

Last updated on OCTOBER 13, 2022

Applies to:

Symptoms

On a Sun ZFS Storage 7420, NBU backups using a direct attached IBM Ultrium 5 drive could fail, while backups via network are run successfully.

Tests writing to and reading from the drive with tar succeeds without problems.

When running the NBU backup we see following entries in /var/ak/logs/system.sys:

Changes

SCSI Stream Commands (SSC-4) has introduced a new data protection feature for tape drives called "Append Only Mode".

This feature causes the drive to prevent the overwrite of data on a cartridge unless the writing application performs a pre-authorization for the overwrite.

Pre-authorization for overwrite is a done with a new SCSI command (Allow Overwrite) that informs the drive that the data block at the current location is going to be overwritten.

Any attempt to overwrite a data block without pre-authorization returns a write protect error.

IBM LTO-5 drives support this feature (even with LTO-4 media).

Once set, LTO-5 drives remain in append mode until power cycled.

Cause

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