Patent ID: 8645635

Claim:
A method for arbitrating a selection of an active storage controller in a multi-requester storage system including an active-passive pair of storage controllers coupled to a plurality of logic units (LUNs) to avoid potential logic unit thrashing occurring as a result of input/output requests sent to said active storage controller during a change over period in which said active storage controller is swapped for a passive storage controller, said method comprising: in response to a detection that each of a first requester and a second requester has usable access to both a first storage controller and a second storage controller of said active-passive pair of storage controllers: collectively selecting, via arbitration by said first and second requesters, said first storage controller as said active storage controller and said second storage controller as said passive storage controller for a first portion of logic units (LUNs) and said second storage controller as said active storage controller and said first storage controller as said passive storage controller for a second portion of LUNs; in response to a detection that said first requester and said second requester both have usable access to only said first storage controller: communicating to said first requester, by said second requester, that said second requester only has usable access to said first storage controller, communicating to said second requester, by said first requester, that said first requester only has usable access to said first storage controller, and collectively selecting said first storage controller as said active storage controller by said first and second requesters; and in response to a detection that said first requester has usable access only to said first storage controller and said second requester has usable access only to said second storage controller: communicating to said second requester, by said first requester, that said first requester only has usable access to said first storage controller, communicating to said first requester, by said second requester, that said second requester only has usable access to said second storage controller, enabling only one of said first requester and said second requester to select which of said first and second storage controllers as said active storage controller, and selecting, by said enabled first requester or second requester, said first storage controller or said second storage controller as said active storage controller.