NetBackup 7.0.1 is not yet fully compatible with the new structures of the Agile paths on HP-UX 11.31 Itanium edition. As a result, when NetBackup 7.0.1 is installed as a media server and IBM LTO drives are used with the IBM ATDD driver, on closing out the last backup fragment, the ATDD driver will fail to correctly write the End Of Tape (EOT) marker after the empty backup header.
Explanation of how the problem occurs:
- BPTM ends the backup data fragment with a EOF (End Of File) mark
- BPTM then writes an empty header of 1024 bytes after the EOF mark
- BPTM closes the tape and the tape drive
- The ATDD tape device driver writes an EOT (End of Tape) mark of 0 bytes
At the end of the last backup fragement written, BPTM reads the position on the tape using the pass through path instead of ATDD driver and subtracts two to confirm tape block position of the last backup fragment written.
The error "External event caused rewind during write" occurs because the BPTM position check at the end of the backup calculates one block less of where it expects the tape position to be for the last fragment. There should be the empty NetBackup header and a EOT filemark written by the ATDD tape driver on device close (which is missing).
More detail on the error can be seen with the scsi_command -map output and a BPTM log extract.
scsi_command -map output
00009258: file 5: record 1: size 1024: NBU BACKUP header
backup_id system_1285254049: frag 1: file 4: copy 1
expiration 1285858849: retention 0: block_size 262144
flags 0x0: mpx_headers 0: resume_count 0: media 000009
00009259: file 5: record 2: size 262144
00009885: file 5: eof after 627 records: 164103168 bytes
00009886: file 6: record 1: size 1024: NBU EMPTY header (file 5)
This is an example output showing when the driver writes the filemark correctly.
00039383: file 16: record 1: size 1024: NBU TIR header
backup_id system_1285156950: frag -1: file 15: copy 1
expiration 1285761750: retention 0: block_size 262144
flags 0x4: mpx_headers 0: resume_count 0: media 000005
expected size 1577533
00039384: file 16: record 2: size 262144
00039390: file 16: record 8: size 5120
00039391: file 16: eof after 8 records: 1579008 bytes
00039392: file 17: record 1: size 1024: NBU EMPTY header (file 16)
00039393: file 17: eof after 1 records: 1024 bytes
00039394: file 18: eof after 0 records: 0 bytes << REQUIRED <<
NOTE: There is an extra file of 0 bytes written by the tape device driver on device close at the end of the last backup EOF marker.
Using the ATDD driver with NetBackup 7.0.1 and later on HP-UX 11.31 IA64 requires atdd driver 220.127.116.11 or later.
Upgrade to the latest ATDD driver available resolves the problem.
If ATDD driver cannot be upgraded, there is a BPTM Hotfix available from Etrack 2142743 to the HP-UX 11.31 Itanium for NetBackup 7.0.1.
NOTE: The IBM ATDD driver version 18.104.22.168 still has an issue with the latest HP-UX 11.31 OS structures and the Hotfix provided by Etrack 2142743 reverts NetBackup 7.0.1 back to using the older OS structures.
HP-UX 11.31 Itanium Edition
IBM LTO Tape drives
IBM ATDD driver version 22.214.171.124 as per the Symantec NetBackup Hardware Compatibility List