Patent ID: 7788244

Claim:
A method for copying a source snapshot tree to a target snapshot tree, the method comprising: inactivating the source snapshot tree to prevent access to the source snapshot tree; creating a data-structure framework to represent the target snapshot tree; making the target snapshot tree immediately available for storage access by a host computer even though the target snapshot tree does not yet contain data; launching a background-copy process to copy data from the source snapshot tree to the target snapshot tree; and when the background-copy process has completed, making the source snapshot tree again available for access, wherein the source snapshot tree and target snapshot tree each comprises: a linked list of logical devices that include a top logical device that is a source logical device for snapshot operations; and snapshot logical devices generated from the source logical device ordered in reverse order with respect to time of creation, with a first-created snapshot logical device occupying the bottom-logical-device position; and wherein a second logical device closer, in the linked list, to the top logical device than a first logical device is a successor logical device with respect to the first logical device with respect to the first logical device and a third logical device closer, in the linked list, to the bottom logical device than the first logical device is a predecessor logical device with respect to the first logical device.