The invention provides a method for computing the appropriate capacity of a journal volume based on the operating patterns of backup and recovery performed by the user, and composing a recovery system that enables recovery to be performed in a short time using journals. The invention provides a computer system comprising a storage system 120 having a volume 124, a managing computer 100 and a host computer 110, wherein the storage system 120 retains a journal of data stored in the volume and a volume replicating the data stored in the volume, and restoring a volume data at any update time point based on the journal and the replicated volume, and upon receiving operation from a user regarding the volume retaining the journal, the managing computer 100 acquires a registration creation demand including a recovery time objective which is the time to be restored and/or a recovery point objective which is the recovery time point and a journal retention period which is the period for retaining the journal, monitors the journal of data stored in the volume, computes the quantity of the journal, and determines the capacity of the volume for retaining the journal.