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Appendix B. Using DS8000 with iSeries 395
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.