US Patent 9178860 Out-of-path, content-addressed writes with untrusted clients

A method in data storage involves receiving at a metadata server from a client device a BEGIN_WRITE request identifying data to be written by hashes, consulting, by the metadata server a deduplication table to determine historical nature of the data determined to be written, determining that the data was never previously written, was previously written by another client, or was previously written but failed a verification, sending to the client device write locations with tokens for the data, starting an authentication timer, and authorizing the client device to write directly to the data server using the authentication tokens and the authenticated write locations, determining that the data was previously written by the same client, or that the data was previously written and passed the verification test, notifying the client of this circumstance, and receiving from the client device an END_WRITE request.