Patent ID: 8719523

Claim:
A computer system for maintaining instant virtual copies, comprising: a processor; and a storage device connected to the processor, wherein the storage device has stored thereon a program, and wherein the processor is configured to execute instructions of the program to perform operations, wherein the operations comprise: in response to receiving a request to perform an instant virtual copy operation to create an instant virtual copy from a first source volume to a first target volume, creating a first intermediate volume, a first intermediate map, and a first map for the first target volume; making the first intermediate volume dependent on the first source volume in a dependency chain based on the first intermediate map; and making the first target volume dependent on the first intermediate volume in the dependency chain based on the first map; receiving a request to perform another instant virtual copy operation to create an instant virtual copy from the first source volume to a second target volume; in response to determining that the first source volume has not been modified since a last instant virtual copy operation from the first source volume has been performed, making the second target volume dependent on the first intermediate volume in the dependency chain based on a second map; and in response to determining that the first source volume has been modified since a last instant virtual copy operation from the first source volume has been performed; creating a second intermediate volume, a second intermediate map, and a third map for the second target volume; making the second intermediate volume dependent on the first source volume in the dependency chain based on the second intermediate map; and making the second target volume dependent on the second intermediate volume in the dependency chain based on the third map.