System and method for cascading data updates through a virtual copy hierarchy
View Patent ↗A system and method for managing data updates by cascading those updates through a virtual copy hierarchy from parent copies to child copies are provided. Virtual copies are created and managed through the use of an instant copy mechanism. Metadata subsets manage both the original data and the copies created by the instant copy mechanism. With an exemplary embodiment of the system and method, changes made to one copy of the data are cascaded to all child copies of the data. In this paradigm not only is the metadata entry for one particular copy changed, but also the corresponding metadata entries of any copies descended from that copy. In an exemplary method, a tree structure is used to maintain a record of all metadata table subsets created by use of an instant copy method. The tree structure can then be searched to find all child copies of a particular copy.
1. A method, in a data processing system, for updating metadata in a hierarchy of copies of metadata, comprising:
updating a first copy of metadata;
identifying a second copy of metadata that is a child copy of the first copy of metadata;
updating the second copy of metadata, in response to the updating of the first copy of metadata, to be consistent with the update to the first copy of metadata; and
wherein the first copy of metadata has a parent copy of metadata, and wherein the parent copy of metadata is not updated in response to the updating of the first copy of metadata.
2. The method of claim 1 , wherein updating the first copy of metadata is performed in response to a request to modify data in a physical data storage location.
3. The method of claim 2 , wherein updating the first copy of metadata includes:
copying the data in the physical data storage location to a new physical data storage location; and
modifying the first copy of metadata to point to the new physical data storage location.
4. The method of claim 3 , wherein updating the second copy of metadata includes modifying the second copy of metadata to point to the new physical data storage location.
5. The method of claim 1 , wherein identifying a second copy of metadata that is a child copy of the first copy of metadata includes accessing a hierarchical data structure used to track copies of metadata.
6. The method of claim 5 , wherein the hierarchical data structure stores information about copies of metadata including whether the copy of metadata is a parent to another copy of metadata and whether the copy of metadata is a child of another copy of metadata.
7. The method of claim 6 , wherein the hierarchical data structure further stores information regarding the location of each copy of metadata.
8. The method of claim 1 , wherein the second copy of metadata is an instant copy of the first copy of metadata.
9. A computer program product stored on a computer readable medium for updating metadata in a hierarchy of copies of metadata, comprising:
first instructions for updating a first copy of metadata;
second instructions for identifying a second copy of metadata that is a child copy of the first copy of metadata;
third instructions for updating the second copy of metadata, in response to the updating of the first copy of metadata, to be consistent with the update to the first copy of metadata; and
wherein the first copy of metadata has a parent copy of metadata, and wherein the parent copy of metadata is not updated in response to the updating of the first copy of metadata.
10. The computer program product of claim 9 , wherein the first instructions for updating the first copy of metadata include:
instructions for copying the data in the physical data storage location to a new physical data storage location; and
instructions for modifying the first copy of metadata to point to the new physical data storage location.
11. The computer program product of claim 10 , wherein the third instructions for updating the second copy of metadata include instructions for modifying the second copy of metadata to point to the new physical data storage location.
12. The computer program product of claim 9 , wherein the second instructions for identifying a second copy of metadata that is a child copy of the first copy of metadata include instructions for accessing a hierarchical data structure used to track copies of metadata.
13. The computer program product of claim 12 , wherein the hierarchical data structure stores information about copies of metadata including whether the copy of metadata is a parent to another copy of metadata and whether the copy of metadata is a child of another copy of metadata.
14. The computer program product of claim 13 , wherein the hierarchical data structure further stores information regarding the location of each copy of metadata.
15. The computer program product of claim 14 , wherein the location of each copy of metadata includes at least one location that is in a different device from the data processing system, and wherein the third instructions for updating the second copy of metadata include instructions for sending an instruction to the different device to update the second copy of metadata.
16. The computer program product of claim 9 , wherein the second copy of metadata is an instant copy of the first copy of metadata.
17. An apparatus in a data processing system for updating metadata in a hierarchy of copies of metadata, comprising:
said data processing system including a processor executing code for updating a first copy of metadata;
a data structure for identifying a second copy of metadata that is a child copy of the first copy of metadata;
an update cascade module for updating the second copy of metadata, in response to the updating of the first copy of metadata, to be consistent with the update to the first copy of metadata; and
wherein the first copy of metadata has a parent copy of metadata, and wherein the parent copy of metadata is not updated in response to the updating of the first copy of metadata.