I think that you have two MSA30 with DualBus SCSI Partnumber 302970-B21. One Bus for Disk 1 - 7 and the other for Disk 8 - 14. Look at the Backend of the MSA30. There should be two SCSI connetors.
Your MSA1000 has only two SCSI Connectors at the Backend. So you can attach two Single Bus MSA 30 or one Dual Bus MSA 30 to use all the drives.
You can change the MSA I/O Modul. The Single Bus I/O Modul is Partnumber 287484-B21. With this Modul all Disk are on the same Bus. Then you can use all 42 Drives.
Best Regards
Thomas