Patent ID: 8219529

Claim:
A method for retention of active data in a storage server having a first data image and a disk storage containing an aggregate storage of data elements for a first storage volume, the first data image being an image of a subset of the data elements of the disk storage, wherein the first data image indexes the data elements of the disk storage in a first manner, and the first storage volume being a mirror of a second storage volume, the method comprising: generating, by a storage server in response to receiving an update for the first storage volume, a second data image to mirror the update in the second storage volume; receiving a request for a data element; determining whether the requested data element is contained in the second data image; determining whether the requested data element is contained in a container file of the first storage volume if the requested data element is not contained in the second data image, wherein the container file indexes the data elements of the disk storage in a second manner; and obtaining the requested data from one of the container file and the disk storage depending on whether the requested data is contained in the container file, wherein indexing the data elements of the disk storage in the first manner comprises indexing by a volume identification, a snapshot identification, a file identification, and a file block number and the indexing the data elements of the disk storage in a second manner comprises indexing by a virtual indexing structure using virtual block numbers.