IBM DS8000 manual Multipath rules for multiple iSeries systems or partitions

Figure B-33 Multipath connections

Multipath rules for multiple iSeries systems or partitions

When you use multipath disk units, you must consider the implications of moving IOPs and multipath connections between nodes. You must not split multipath connections between nodes, either by moving IOPs between logical partitions or by switching expansion units between systems. If two different nodes both have connections to the same LUN in the DS8000, both nodes might potentially overwrite data from the other node.

The system enforces the following rules when you use multipath disk units in a multiple-system environment:

￿If you move an IOP with a multipath connection to a different logical partition, you must also move all other IOPs with connections to the same disk unit to the same logical partition.

￿When you make an expansion unit switchable, make sure that all multipath connections to a disk unit will switch with the expansion unit.

￿When you configure a switchable independent disk pool, make sure that all of the required IOPs for multipath disk units will switch with the independent disk pool.

If a multipath configuration rule is violated, the system issues warnings or errors to alert you of the condition. It is important to pay attention when disk unit connections are reported missing. You want to prevent a situation where a node might overwrite data on a LUN that belongs to another node.

Appendix B. Using DS8000 with iSeries 395