According to IBM:
Drive performance:
        Native sustained data rate
                B: 2.2MB/sec
                C: 7.0MB/sec
        Compressed sustained data rate
                B: 6.6MB/sec (3:1)
                C: 15.0MB/sec (maximum)
        SCSI burst data rate 20MB/sec
Capacity
        Per cartridge 5GB up to 15GB (with 3:1 LZ1 compression)
        Per 3570 library 100GB up to 300GB (with 3:1 LZ1 compression)

I have done testing here and we achieve from the ADSM server to the Magstar
3570 a aggregate tranfer rate of approx 1MB/Sec. There are better/faster
tape subsystems to buy.

Hope this helps.