Patent ID: 9483481
Filing Date: 2016-11-01
CPC Classification: G06F

Claim Text:
1. A computer-implemented method for transferring a portion of a file stored in a non-transitory content addressable storage (CAS) system to a second non-transitory computer readable storage medium, the computer-implemented method comprising: retrieving, in response to a request for the portion of the file, first tree data from a first node in a hash tree that represents the file, the first tree data including a first hash tree depth, a first CAS signature, a block size and a file size, wherein the first node represents a set of data blocks corresponding to the portion of the file; selecting, based on the tree data, a second node from a higher level in the hash tree, wherein the second node represents a subset of data blocks represented by the first node; retrieving second tree data from the second node of the hash tree that represents the file, the second tree data including a second CAS signature; determining that the second CAS signature matches a reserved CAS signature, wherein the reserved CAS signature represents one or more unallocated data blocks; and providing, to the second non-transitory computer readable storage medium and in response to the request, and in response to determining the second CAS signature matches the reserved CAS signature, an indication that the file contains one or more unallocated data blocks; transferring a set of data blocks corresponding to the requested portion of the file from the CAS system and to the second non-transitory computer readable storage medium, wherein the set of data blocks does not include the subset of data blocks corresponding to the second node and encoded with the reserved CAS signature; receiving another request for another portion of the file; retrieving, based on the another request, third tree data from a third node of the hash tree that represents the another portion of the file, the third tree data including a third CAS signature; determining that the third CAS signature does not match the reserved CAS signature; and transferring, in response to determining the third CAS signature does not match the reserved CAS signature, a data block for the another portion of the file from the CAS system to the second non-transitory computer readable storage medium.