Methods and infrastructure for performing repetitive data protection and a corresponding restore of data

A method for restoring data of a block oriented data object comprising several indexed segments by using undo-log information generated and stored as described by:

• setting a set of timestamps tk for a first undo-log journal j0 by a timer k;
• recording each first data modification of a segment that occurs after a timestamp tk has been set by storing old data contents of said segment together with a segment index j and a timestamp tk as an undo-log block in the first undo-log journal j0 before overwriting said segment with modified new data such that the first undo-log journal j0 comprises sequential undo-log blocks corresponding to each timestamp tk;
• transmitting an undo-log block to one or more additional undo-log journals ji based on a timestamp tk and storing redundant undo-log information in the one or more additional undo-log journals, the redundant undo-log information comprising a subset of undo-log blocks from the first undo-log journal, such that each additional undo-log journal comprises sequential undo-log blocks written for a different set of timestamps tk/i, a granularity of timestamps and corresponding undo-log blocks in an additional undo-log journal decreasing such that each additional undo-log journal comprises fewer undo-log blocks than a previous undo-log journal, wherein each undo-log journal ji represents a different time graining of undo-log information and wherein the density of the corresponding timestamps tk/i decreases with increasing i;
• and
• restoring data contents of the segment to a state before a timestamp t using a sequence of undo-log blocks each selected from an undo-log journal with a coarsest available granularity for the undo-log block such that the undo-log blocks in the sequence are selected from multiple undo-log journals, the restoring comprising,
• reading a last undo-log journal jN-1, the last undo-log journal jN-1 having the fewest number of undo-log blocks relative to the first undo-log journal j0 and the other additional undo-log journals ji, starting from the first undo-log block comprising a first timestamp tk/N-1 which is the same as or occurs after a time for undo-log journal jN-1 which corresponds to timestamp t, till the end of undo-log journal jN-1,
• reading the next journal ji in decreasing order starting from the first undo-log block, comprising the first timestamp tk/i which is the same as or occurs after the time for undo-log journal ji which corresponds to timestamp t, till the undo-log block comprising the first timestamp tk/i which is the same as or occurs after the first timestamp for undo-log journal ji which corresponds to the timestamp tk/i+1 of undo-log journal ji+1 having been read of the preceding undo-log journal ji+1;
• repeating the preceding step of reading for all next journals ji−1 such that the data stored in an undo-log block read from an undo-log journal is only written to the corresponding segment of the data object, if said segment has not been re-written before, initiated by an undo-log block read before from the same undo-log journal.

A method for restoring data of a block oriented data object comprising several indexed segments by using undo-log information generated and stored as described by:

• setting a set of timestamps tk for a first undo-log journal j0 by a timer k;
• recording each first data modification of a segment that occurs after a timestamp tk has been set by storing old data contents of said segment together with a segment index j and a timestamp tk as an undo-log block in the first undo-log journal j0 before overwriting said segment with modified new data such that the first undo-log journal j0 comprises sequential undo-log blocks corresponding to each timestamp tk;
• transmitting an undo-log block to one or more additional undo-log journals ji based on a timestamp tk storing redundant undo-log information in the one or more additional undo-log journals, the redundant undo-log information comprising a subset of undo-log blocks from the first undo-log journal, such that each additional undo-log journal comprises sequential undo-log blocks written for a different set of timestamps tk/i, a granularity of timestamps and corresponding undo-log blocks in an additional undo-log journal decreasing such that each additional undo-log journal comprises fewer undo-log blocks than a previous undo-log journal, wherein each undo-log journal ji represents a different time graining of undo-log information, wherein the density of the corresponding timestamps tk/i decreases with increasing i;
• and
• restoring data contents of the segment to a state before a timestamp t using a sequence of undo-log blocks each selected from an undo-log journal with a coarsest available granularity for the undo-log block such that the undo-log blocks in the sequence are selected from multiple undo-log journals, the restoring comprising:
• reading the first undo-log journal j0, the first undo-log journal j0 having the highest number of undo-log blocks relative to the additional undo-log journals ji starting from a first undo-log block, comprising a first timestamp tk/i which is the same as or occurs after timestamp t, till the first undo-log block comprising a timestamp tk/i which is the same as or occurs after a first timestamp tk/i+1 of a next undo-log journal ji+1, with timestamp tk/i+1 which is the same as or occurs after timestamp t;
• repeating the preceding step of reading for all next undo-log journals ji+1 with i=1, . . . , N−2;
• reading a last undo-log journal jN-1 starting from the first undo-log block comprising the first timestamp tk/N-1 which is the same as or occurs after timestamp t, till the end of undo-log journal jN-1, such that the data stored in an undo-log block read from an undo-log journal is only written to the corresponding segment of the data object, if said segment has not been re-written before, initiated by an undo-log block read before from the same undo-log journal.

A method for performing repetitive data protection for data stored in a block oriented data object comprising several indexed segments, the method comprising:

• setting a different granularity of timestamps for each of a plurality of undo-log journals such that the granularity of the timestamps decreases for each undo-log journal between a first undo-log journal and a last undo-log journal;
• recording, for each undo-log journal from the plurality of undo-log journals, each first data modification of a segment that occurs after a timestamp for the undo-log journal by storing old data contents of the segment, a segment index of the segment, and the timestamp as an undo-log block in the undo-log journal such that each undo-log journal from the plurality of undo-log journals comprises sequential undo-log blocks corresponding to the granularity of timestamps for the undo-log journal, each undo-log journal between the first undo-log journal and the last undo-log journal comprising fewer undo-log blocks than a previous undo-log journal based on the different granularity of timestamps for each undo-log journal;
• and
• restoring data contents of the segment from a state of the data contents at a start time to a state of the data contents at a target time using a sequence of undo-log blocks from two or more of the plurality of undo-log journals, the undo-log blocks in the sequence selected from one of the two or more undo-log journals with a coarsest available granularity for the undo-log block such that the undo-log blocks in the sequence are selected from each of the two or more undo-log journals.