Determine whether you want input/output adapter (IOA) level protection based on the following:
- To keep your system available when an IOA fails.
- To concurrently repair a failed disk unit or IOA. To use problem recovery procedures in preparation for isolating a failing item or to verify a repair action, the IOA must be dedicated to the repair action. If any disk units that are attached to the IOA do not have IOA-level protection, then this part of concurrent maintenance is not possible.
To achieve IOA-level protection, all disk units must have a mirrored unit attached to a different IOA. This figure shows IOA-level protection. The two storage units make a mirrored pair. With IOA-level protection, the system can continue to operate if one IOA fails. If the I/O processor fails, the system cannot access data on either of the disk units, and the system is unusable.
This figure shows the elements of IOA-level protection: one bus, connected to one I/O processor, connected to two IOAs, which are each attached to a separate disk unit.