Abstract: A novel hierarchical storage architecture called SSD HD MO is presented, which uses a small portion of a hard drive in a log structure format referred to as cache disk and solid state disk（SSD） technology on magneto optic （MO） to implement a high performance second storage system. SSD HD MO takes advantage of large data transfer sizes and uses inexpensive disk space to provide a low cost and reliable caching solution.Trace driven simulation experiments are carried out to evaluate the performance of the proposed disk architecture. Under the office/engineering work load environment, the SSD HD MO shows superb disk performance for writes as compared to the existing MO systems. Furthermore, SSD HD MO is very reliable and works at the device or device driver level. As a result, it can be applied directly to current file systems without the need of changing the operating system.