A single stream read-out from DR can get 100-120 MB/s on CIFS, but should get to ~300 MB/s single stream readout using OST.
On multiple stream readout, it should go to 400 MB/s on both CIFS and OST.
In NetBackup, there is a buffer tuning parameter that may need to be increased. In an example use case scenario, after increasing the NetBackup tuning parameter NUMBER_DATA_BUFFERS to 256 up from the default of 32, single stream speeds went from 100 MB/s to full LTO7 speeds (~300 MB/s).
Please see the following link for more details on changing the NetBackup NUMBER_DATA_BUFFERS parameter:
https://www.veritas.com/support/en_US/article.100008276