A storage controller for a storage system in which there are multiple storage devices and a method for recording diagnostic information are provided. The storage controller includes a storage device manager which has means for allocating a storage device in the storage system for storing diagnostic data. The storage controller also includes means for generating diagnostic data regarding the operation of the storage controller. Two buffers are used for alternately recording and writing batches of diagnostic data to the allocated storage device. The allocated storage device may be a storage device which is normally reserved for disaster recovery in the storage system.