Methods and structure are provided for cache load balancing in storage controllers that utilize Solid State Drive (SSD) caches. One embodiment is a storage controller of a storage system. The storage controller includes a host interface operable to receive Input and Output (I/O) operations from a host computer. The storage controller also includes a cache memory that includes an SSD. Further, the storage controller includes a cache manager that is distinct from the cache memory. The cache manager is able to determine physical locations in the multiple SSDs that are unused, to identify an unused location that was written to a longer period of time ago than other unused locations, and to store a received I/O operation in the identified physical location. Further, the cache manager is able to trigger transmission of the stored I/O operations to storage devices of the storage system for processing.