DETECTING SERVER PAGES WITHIN BACKUPS
Segmentation of a backup or a backup stream. A backup is segmented using a window that is sized to correspond to a size of a header portion of a page of a database. The data in the window is evaluated to determine whether the data matches header criteria. The data may be evaluated with a stronger check as well. If the checks are positive or true, a page is located and subsequent pages can be located by advancing the window by the page size.
1 . A method for segmenting a backup, the method comprising:
positioning a window over a portion of the backup, wherein the window identifies data of the backup;
performing a first check between portions of the identified data in the window and expected values for the portions of the identified data;
determining that the window corresponds to a header of a page when the first check is positive; and
determining a location of the page in the backup.
2 . The method of claim 1 , further comprising determining locations of subsequent pages in the backup based on the location of the page.
3 . The method of claim 1 , further comprising a second check of the page based on the identified data.
4 . The method according to claim 3 , wherein the second check includes comparing a checksum of the page with data in the window corresponding to the checksum.
5 . The method according to claim 1 , wherein the identified data has a size corresponding to a size of a header of the page.
6 . The method according to claim 1 , wherein the first check includes comparing specific portions of the identified data with expected values for the specific portions of the data.
7 . The method according to claim 6 , wherein the expected values include a particular value, a range of values, or a set of values.
8 . The method according to claim 1 , wherein the first check includes a plurality of comparisons, wherein the window corresponds to the header of the page when all of the plurality of comparisons are true.
9 . The method according to claim 1 , further comprising moving the window when the first check fails such that the window identifies new data and performing the first check on the new data.
10 . The method according to claim 8 , further comprising comparing data in the window corresponding to a header field, a flag field, a level field, a free count field, a free data field, and a slot count field with expected values, respectively, of the header field, the flag field, the level field, the free count field, the free data field, and the slot count field.
11 . The method according to claim 4 , further comprising adjusting at least the first check when the first check fails and the second check succeeds or the first check succeeds and the second check fails, wherein adjusting at least the first check includes at least one of changing expected values for header fields involved in the first check and/or selecting a different combination or header fields used in the first check.
12 . A method for segmenting a backup, the method comprising:
positioning a window over a portion of the backup, wherein the window identifies data of the backup;
performing a first check between portions of the identified data in the window and expected values for the portions of the identified data;
performing a second check on a page that begins with the identified data; and
determining a location of a valid page in the backup when both the first check and the second check are positive.
13 . The method of claim 12 , further comprising determining locations of subsequent pages in the backup based on the location of the page.
14 . The method of claim 13 , wherein only a third check is used to determine the locations of subsequent pages.
15 . The method of claim 14 , wherein the third check is the same as or different from the first check.
16 . The method of claim 15 , wherein the third check includes evaluating a page identifier or performing a plurality of comparisons between data in the window with expected values of the data.
17 . The method according to claim 12 , wherein the second check includes comparing a checksum of the page with data in the window corresponding to the checksum.
18 . The method according to claim 12 , further comprising advancing the window by a set amount when one of the first check and the second check fails and performing the first check and the second check with respect to new data in the repositioned window.
19 . The method according to claim 12 , wherein the first check includes evaluating expected values of data in the window and evaluating relationships between data in the window.
20 . The method according to claim 12 , wherein the expected values include a particular value, a range of values, or a set of values.
21 . The method according to claim 12 , wherein the window is advanced by a page size when a valid header is located.