Patent ID: 7979401

Claim:
A method comprising: storing a plurality of tokens corresponding to a plurality of data units written to a rewritable file system, wherein an ordering relationship is maintained among the plurality of tokens, wherein the ordering relationship is such that a first token corresponding to a first data unit is of a lesser numerical value in comparison to a second token corresponding to a second data unit, and wherein the first data unit is written at an earlier point in time in comparison to the second data unit, wherein the storing of the plurality of tokens further comprises: writing, in a first set of data structures, timestamps in association with the plurality of data units, wherein a timestamp indicates a chronological time at which a data unit is written; and generating, and writing in a second set of data structures, the plurality of tokens with numerical values in a monotonically increasing order as the plurality of data units are written into the rewritable file system; and reverting the rewritable file system to an indicated point in time based on the ordering relationship that is maintained among the stored plurality of tokens via the numerical values written in the monotonically increasing order in the second set of data structures.