Bus-level protection

Determine if you want bus-level protection.

The bus-level protection has the following benefits:

• Bus failures are rare in comparison to other disk-related hardware failures.
• The system can continue to operate after a bus failure.
• The system cannot operate if bus 1 fails.
• If a bus fails, disk I/O operations may continue, but other hardware is lost (such as work stations, printers and communication lines) making the system unusable.
• Concurrent maintenance is not possible for bus failures.

To achieve bus-level protection, all disk units that are attached to a bus must have a mirrored disk unit attached to a different bus. Bus-level protection is not possible for disk unit 1.

The bus-level protection figure shows the elements of bus-level protection: one expansion unit that contains two buses attached to separate IOPs, IOAs , and disk units, respectively. The two disk units make a mirrored pair.