Speed up the restore

Dear Experts,

We are restoring database from disk media to server. Restore rate is very slow like 6MB/second. We have 1.5TB database. What can we do to speed up the restore?

run{
allocate channel 'dev_0' type 'sbt_tape' parms 'SBT_LIBRARY=/opt/omni/lib/libob2oracle8_64bit.so';
allocate channel 'dev_1' type 'sbt_tape' parms 'SBT_LIBRARY=/opt/omni/lib/libob2oracle8_64bit.so';
allocate channel 'dev_2' type 'sbt_tape' parms 'SBT_LIBRARY=/opt/omni/lib/libob2oracle8_64bit.so';
allocate channel 'dev_3' type 'sbt_tape' parms 'SBT_LIBRARY=/opt/omni/lib/libob2oracle8_64bit.so';
allocate channel 'dev_4' type 'sbt_tape' parms 'SBT_LIBRARY=/opt/omni/lib/libob2oracle8_64bit.so';
allocate channel 'dev_5' type 'sbt_tape' parms 'SBT_LIBRARY=/opt/omni/lib/libob2oracle8_64bit.so';
send device type 'sbt_tape' 'OB2BARHOSTNAME=erpprod-scan.ttd.com';
send channel 'dev_0' 'OB2BARTYPE=Oracle8';
send channel 'dev_0' 'OB2APPNAME=prodcdb2';
send channel 'dev_0' 'OB2BARLIST=ERP_PROD_19C';
send channel 'dev_1' 'OB2BARTYPE=Oracle8';
send channel 'dev_1' 'OB2APPNAME=prodcdb2';
send channel 'dev_1' 'OB2BARLIST=ERP_PROD_19C';
send channel 'dev_2' 'OB2BARTYPE=Oracle8';
send channel 'dev_2' 'OB2APPNAME=prodcdb2';
send channel 'dev_2' 'OB2BARLIST=ERP_PROD_19C';
send channel 'dev_3' 'OB2BARTYPE=Oracle8';
send channel 'dev_3' 'OB2APPNAME=prodcdb2';
send channel 'dev_3' 'OB2BARLIST=ERP_PROD_19C';
send channel 'dev_4' 'OB2BARTYPE=Oracle8';
send channel 'dev_4' 'OB2APPNAME=prodcdb2';
send channel 'dev_4' 'OB2BARLIST=ERP_PROD_19C';
send channel 'dev_5' 'OB2BARTYPE=Oracle8';
send channel 'dev_5' 'OB2APPNAME=prodcdb2';
send channel 'dev_5' 'OB2BARLIST=ERP_PROD_19C';
restore database;
}