Patent ID: 8296265
Filing Date: 2012-10-23
Classification: G06F,Y10S

Abstract:
1. A computer system to be coupled to a host computer via a network, the computer system comprising: a data volume storing write data from the host computer; a snapshot storing area storing a first snapshot of at least a portion of the data volume at a first point in time, and also storing a second snapshot of the portion of the data volume at a second point in time subsequent to the first point in time; and a journal storing area storing journal entries including a journal entry between the first point in time and the second point in time, wherein the computer system manages journal operations to record the journal entries, and monitors the journal storing area so as to free at least one of the stored journal entries in the journal storing area based on a predetermined criterion which enables data recovery by using at least the second snapshot and the stored journal entries, wherein based upon a command for generating marker information from the host computer, the computer system records marker information as being associated with the journal entries in the journal storing area, the marker information being independent of a write request, wherein based upon a command for getting marker information from the host computer, the computer system retrieves the recorded marker information for the host computer, and wherein when receiving a data recovery request specifying a specific one of the marker information representing a third point in time between the first point in time and the second point in time, if the computer system determines that the data recovery request can be performed based on the specific one of the marker information and the stored journal entries, the computer system copies the first snapshot to a recovery volume, selects at least one of the journal entries corresponding to the write operations conducted between the first point in time and the third point in time and recovers data of the portion of the data volume at the third point in time by using at least a portion of the selected at least one journal entry and the copied snapshot in the recovery volume.