Patent ID: 7552276

Claim:
A method for managing a storage server comprising a first cluster of first and second storage controllers controlling first and second storage arrays, and a second cluster of third and fourth storage controllers controlling third and fourth storage arrays, said first cluster including a first cache memory and a first nonvolatile storage (“NVS”) shared by said first and second storage controllers, said second cluster including a second cache memory and a second nonvolatile storage (“NVS”) shared by said third and fourth storage controllers, said method comprising the steps of: determining a level of impairment of access to said first and second storage arrays based on an amount of time that data controlled by said first cluster was held in said first cache memory before being outpaged to said first and second storage arrays, and an amount of requests to access said first and second storage arrays that were delayed due to insufficient first NVS; determining a level of impairment of access to said third and fourth storage arrays based on an amount of time that data controlled by said second cluster was held in said second cache memory before being outpaged to said third and fourth storage arrays, and an amount of requests to access said third and fourth storage arrays that were delayed due to insufficient second NVS; and moving data out of one of said storage arrays based on either or both of the determining steps.