Challenge
All tape write operations fail for MHVTL if the block size on drives differs from 65 KB
Cause
Veeam Backup & Replication v9 has a new algorithm of choosing the block size. Now Veeam automatically detects the highest available block size and runs jobs according to this value. Currently this option is available for all supported devices except MHVTL.
Solution
Manually change the block size in this dialog box:
More Information
Please see Data Block Size section here