I'm using DPM 2012 SP-1 on a Dell PowerEdge R-520 connected to a Dell TL-4000 tape library via an iSCSI bridge (iSCSI to SAS). The tape library is using the most recent Dell (IBM) drivers for both tape library, iSCSI Bridge and tape drives. All tape library functions work except I/O operations. When a protection group is backed up to tape, a tape is selected and moved into one of the two drives. Then nothing happens and after trying two tapes, reports a tape backup error with ID 30101 and I/O device error 0x8007045D. I've made the registry changes for BufferQueueSize, StorPort and BusyRetryCount from http://blogs.technet.com/b/dpm/archive/2012/05/14/things-you-can-do-to-help-data-protection-manager-utilize-your-tapes-full-capacity.aspx without any success.
This is all new equipment and we have never been able to get to write anything to a tape
Firmware version on tape library is the most recent at B.60.