Data Domain: NetBackup 8.1 on Solaris reports error status 84 (media write error)

When running backup jobs on DDVTL LTO-7 drives using NetBackup on Solaris, it fails with the following error.

Error bptm (pid=53194) FREEZING media id 0006L7, too many data blocks written, check tape/driver block size configuration
Info bptm (pid=53194) EXITING with status 84

These error messages are found in the NetBackup log bundle.

The larger I/O operations are split at the driver layer due to st (tape driver) driver config settings.

For a few I/O operations, one NetBackup write resulted into two split blocks writes on DDVTL. Therefore, a mismatch was seen in the block count.

vtcck outputs show that one record of 65536 was split into two records. That is, one record sized 65534 bytes and another sized 2 bytes.

We see that there are two byte-sized records which were created for few of the operations.
 

21 data and 11 filemark records processed
Minimum record size: 2
Maximum record size: 65534
Average record size: 16140
Record Size    Number of Records
         2    1
       1024    11
      32768    8
      65534    1
      good: YES

The workaround is to edit the "st.conf" and reboot.

1. Run the Solaris command # mt config on the DDVTL LTO-7 tape drive.
For example, # mt -f /dev/rmt/0 config

The following result (with the fourth parameter being 0x1065B) indicates that the problem exists.  

tape-config-list =
        "IBM     ULTRIUM-TD7", "IBM     ULTRIUM-TD7", "CFGIBMULTRIUMTD7";
        CFGIBMULTRIUMTD7 = 2,0x3B,0,0x1065B,4,0x00,0x00,0x00,0x00,0,120,120,3600,3600,3600,3600,3600;

2. Edit the Solaris file /kernel/drv/st.conf to include the ST_NO_RECSIZE_LIMIT (0x8000) flag in the "tape-config-list." 

tape-config-list =
        "IBM     ULTRIUM-TD7", "IBM     ULTRIUM-TD7", "CFGIBMULTRIUMTD7";
        CFGIBMULTRIUMTD7 = 2,0x3B,0,0x1865B,4,0x00,0x00,0x00,0x00,0,120,120,3600,3600,3600,3600,3600;

3. Reboot with reconfigure option.

# reboot -- -r