Patent ID: 7096331

Claim:
In a data storage environment having a first volume of data denominated as a source being stored on a data storage system, and a second volume of data denominated as a clone and which has data content that is a copy of data content of the source being stored on the data storage system or on another data storage system, a method of-processing a host computer's request to write data to the source during a restoration of the source, the method comprising the steps of: restoring the source by copying data content from the clone to overwrite the data content of the source; queuing in memory any host computer requests to write or read data for the source that involve data that is being restored from the clone to the source during the queuing process; and copying any data needed to service the host computer requests to write or read data for the source, which step is denominated as a copy on demand step, wherein a map denominated as a copy on demand map is used to track extents being copied during the restoring step and the copy on demand map is used to coordinate the restoring and the copy on demand step to avoid data corruption.