Patent ID: 7085907

Claim:
A method of managing memory in a storage control unit including first and second clusters, each cluster including a processor, NVS memory and cache memory, a portion of each of the NVS memory and cache memory of each cluster allocated to buffers, the method comprising: commencing a dual-cluster initial microcode load (IML) of the storage control unit; determining the size L 1 of the NVS buffer of the cluster having the larger NVS buffer; allocating a portion of the cache of the first cluster to a buffer equal in size to L 1 ; allocating a portion of the cache of the second cluster to a buffer equal in size to L 1 ; determining the size S 1 of the NVS buffer of the cluster having the smaller NVS buffer; completing the dual-cluster IML; initializing the NVS buffers and the cache buffers of the first and second clusters to a size equal to S 1 ; operating the storage control unit in a dual-cluster mode; performing a failback-to-service mode for the first cluster; changing the amount of NVS and cache memory installed in the first cluster; commencing a single-cluster IML of the first cluster; allocating a portion of the NVS of the first cluster to an NVS buffer; determining a new size L 2 of the NVS buffer of the cluster having the larger NVS buffer; allocating a portion of the cache of the first cluster to a buffer equal in size to L 2 ; determining the size S 2 of the NVS buffer of the cluster having the smaller NVS buffer; commencing a failback-to-dual mode of the storage control unit; initializing the NVS buffers and the cache buffers of the first and second clusters to a size equal to S 2 ; and operating the storage control unit in the dual-cluster mode.