Block status mapping system for reducing virtual machine backup storage
Systems and methods programmatically determine the status of blocks in a virtual machine image. In certain embodiments, the system can determine which blocks are active, deleted, zero, or a combination of the same. In certain embodiments, the system advantageously determines block status without scanning all the blocks in a virtual machine image. Instead, the system can access metadata in a file system of a virtual machine image to determine the block status. When backing up the virtual machine image, the system can back up active blocks while skipping inactive blocks, including deleted and/or zero blocks. As a result, the system can take less time to back up a virtual machine image, and the resulting backup file or files can consume less storage space.
1. A system for backing up a virtual machine image, the system comprising:
a computer system comprising computer hardware, the computer system programmed to implement:
a mapping module configured to:
access a virtual machine image comprising a file system of a guest operating system of a virtual machine to obtain metadata about the file system, the metadata stored within the virtual machine image, the metadata describing logical or physical structure of the file system, wherein the mapping module is configured to obtain the metadata from the virtual machine image without executing inside the virtual machine,
obtain from the metadata an indication of status of blocks in the file system,
store the status of at least some of the blocks in a map data structure, wherein the map data structure is stored outside the virtual machine image; and
a backup module located outside the virtual machine image and configured to back up active blocks of the virtual machine image by at least:
accessing the map data structure to determine the status of the at least some of the blocks, wherein a block in the file system is determined to have an active status if the block includes non-zero data or non-deleted data, wherein a block in the file system is not determined to have an active status if the block includes deleted data;
wherein, for purposes of the accessing, data that has been marked by the guest operating system as deleted but that has not been erased from storage is considered deleted data, and
backing up the blocks that have an active status while not backing up the blocks that do not have an active status, to thereby reduce backup storage consumption and backup time.
2. The system of claim 1 , wherein the mapping module is further configured to store the status of at least some of the blocks in the map data structure by storing a bit representing the status for each of the blocks.
3. The system of claim 1 , wherein the status for a given one of the blocks is selected from the group consisting of active and deleted.
4. The system of claim 1 , wherein the status for a given one of the blocks is selected from the group consisting of active, deleted, and zero.
5. The system of claim 1 , wherein the status for a given one of the blocks is selected from the group consisting of active and inactive.
6. The system of claim 1 , wherein the map data structure comprises a bitmap.
7. The system of claim 1 , wherein the metadata comprises a Master File Table.
8. The system of claim 1 , wherein the metadata comprises one or more inodes.
9. A method of backing up a virtual machine image, the method comprising:
by a computer system comprising computer hardware:
accessing a virtual machine image comprising a file system of a guest operating system of a virtual machine executing on a host server;
identifying deleted blocks of the file system without reading the deleted blocks, said identifying comprising accessing metadata included within the file system to determine which blocks of the file system are the deleted blocks;
wherein the deleted blocks comprise blocks that have been marked as deleted by the guest operating system but that have not been erased from storage; and
backing up the virtual machine image by at least storing active blocks of the file system in computer storage while not backing up the deleted blocks.
10. The method of claim 9 , wherein said accessing the virtual machine image comprises using an application programming interface (API) to access the virtual machine image.
11. The method of claim 10 , further comprising using the API to access the metadata in the file system.
12. The method of claim 9 , wherein said accessing the metadata of the file system comprises searching the virtual machine image at a predetermined location to identify the metadata.
13. The method of claim 9 , further comprising identifying temporary blocks associated with temporary files of the file system.
14. The method of claim 13 , wherein said backing up the virtual machine image further comprises skipping the temporary blocks.
15. The method of claim 9 , wherein said identifying the deleted blocks is performed by a component executing outside of the virtual machine.
16. A non-transitory computer-readable storage medium comprising computer-executable instructions configured to implement a method of backing up a virtual machine image, the method comprising:
initiating a backup of a virtual machine configured to execute on a host server, the virtual machine comprising a guest operating system and a file system associated with the guest operating system, the file system including active blocks that are in use by the virtual machine and deleted blocks, the deleted blocks comprising blocks that are marked as deleted by the guest operating system but are not erased from storage;
identifying the deleted blocks and the active blocks of the file system without scanning all blocks of the file system, said identifying being performed by a component executing outside of the virtual machine; and
backing up the active blocks of the file system while not backing up the deleted blocks of the file system.
17. The non-transitory computer-readable storage medium of claim 16 , wherein said identifying the one or more of deleted blocks and active blocks comprises storing an indication of deleted status of the deleted blocks in a data structure stored outside of the virtual machine.
18. The non-transitory computer-readable storage medium of claim 16 , wherein said identifying the one or more of deleted blocks and active blocks comprises storing an indication of active status of the active blocks in a data structure.
19. The non-transitory computer-readable storage medium of claim 16 , further comprising restoring the virtual machine image subsequent to said backing up, said restoring comprising writing zero blocks to a restore file.
20. The non-transitory computer-readable storage medium of claim 19 , wherein said restoring further comprises overwriting at least some of the zero blocks with the active blocks.