The present invention relates to a storage system, including a first storage unit having a first storage volume for storing data, and a second storage unit having a second storage volume communicably connected with the first storage unit, wherein the first storage unit further comprises a replication data transmission unit for transmitting the replication of data to a second storage unit when the data is written to the first storage volume, the second storage unit further comprises a replication data reception unit for writing the replication of the data transmitted by the replication data transmission unit to the second storage volume, the first storage unit further comprises a disk heart beat write unit for repeatedly writing a first heart beat message to the first storage volume at intervals within a predetermined time, and the second storage unit further comprise a disk heart beat detection unit for detecting the replication of the first heart beat message to be written to the second storage volume by the replication data reception unit.