I have 3 media servers sharing 2 drives in an Quantum i500.
We have a Storage lifcycle policy which eventually write to these 2 drives.
There are 2 active jobs however they will only write to one drive at a time.
One job will be writing and the other active job states "No drives avaiable" and doesn't use the second drive.
Both drives are working ok as the jobs flip between the 2 drives.
Storage Unit has maximum write drives set to 2.
What is the setting of target volume pool for this property: max partially full??
Check also in SLP Parameters Tape resource Multiplier (in master server properties)