Patent ID: 7574462

Claim:
A storage system coupled to a host computer via a network, the storage system comprising: a data volume storing write data from the host computer; a snapshot storing area storing at least one snapshot of at least a portion of the data volume at a point in time when said at least one snapshot is taken; and a journal volume storing journal entries, wherein the storage system monitors an amount of free space on the journal volume, and stops the storing of journal entries when the free space falls below a threshold value, thereby avoiding journal overflow, wherein said threshold value includes a first indication of a lowest amount of free space of capacity of the journal volume, wherein the storage system switches to bitmap management by using a bitmap representation of storage areas in the data volume to track the storage areas in the data volume to which the write operations are directed until additional capacity is provided for the journal volume, wherein the storage system stores a new journal entry in the journal volume following adding of capacity by taking a logical snapshot, wherein taking a logical snapshot includes deleting any stored journal entries corresponding in the bitmap to the new journal entry.