I have had some problems with using tape libraries to work with DPM Server 2007.
Here is a response from Quantum after i spoke to them today.
"I spoke to my consultant about the problem you had regarding Windows servers grabbing resources away from the DPM server, as such, the DPM server could not detect and utilize the tape library resources.
One of the unique features of the Scalar i500 is that we have an I/O blade option that can be integrated into the Si500. This I/O blade can “mask off” or does LUN mapping, it can “dedicate” its resources to be only seen by the DPM server or servers that you allocate the resources to. This is even more secure than zoning on your FC switches!
In addition, the I/O blade can also achieve World-Wide-Name (WWN) and serial number spoofing. As you know, all fibre channel devices have unique WWN and all tape drives have unique serial numbers. Whenever a tape drive is faulty, we will change the tape drive and replace it with another unique WWN and serial number.
This requires your DPM server to “reboot”, and sometimes downtime for reboot is a luxury. With this feature, the I/O blade assumes the old WWN and serial number of the tape drive, spoofing the DPM server that nothing has been changed. "
Hope that helps to all of you who are having issues with tape libraries to work with DPM Server 2007