How does this happen? Surely it depends on the host initiator failover mode setting on the Clariion? (I assume other arrays have a similar setting)
See https://community.emc.com/docs/DOC-12817 (which is out of date as it doesn't mention failover mode 4, which is ALUA)
So, if your failover mode was set to 0 then yes, it could cause trespass ("If Auto-Trespass is enabled on the LUN, the non-owning SP will report that the LUN exists and is available for access. The LUN will trespass to the SP where the I/O request is sent.").
But surely not if it's 1 ("Any I/O request that is made to the non-owning SP will be rejected. A Test Unit Ready (TUR) command sent to the non-owning SP will return with a status of device not ready.")
And actually I just found the following text that seems to suggest that ALUA is a bad idea for Round Robin (although I suppose this depends whether you class Round Robin as "load balancing" or not...): "Load balancing acrossoptimal and non-optimal paths is not recommended, and is only supported in failover situations." (page 6 of http://www.emc.com/collateral/hardware/white-papers/h2890-emc-clariion-asymm-active-wp.pdf)
So what is the technical basis for the "Round Robin must be done in conjunction with ALUA" thing?
