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LUN Path Failover Conditions

Ever wonder what condition caused your ESX server to fail a LUN over to another path? VMware has written a detailed KB article about this and cited examples for each scenario:

http://kb.vmware.com/kb/1003433

The main 4 conditions are:

NO_CONNECT

ILLEGAL_REQUEST

NOT_READY

INTERNAL ERROR

The majority of these conditions are exclusive to Active/Passive arrays (MRU policy) as only 1 controller can have ownership of a LUN. The only failover condition of the above mentioned for the Fixed multipathing policy is a NO_CONNECT.

The list of failover conditions in this KB is not entirely complete as there are some vendor specific codes that would cause a failover that aren’t mentioned here but are built into the multipathing code.