	US 7,603,397 B1
	Detecting and managing missing parents between primary and secondary data stores
Carl F. Hagerstrom, Boulder, Colo. (US); Thomas Dixon Hutchinson, Boulder, Colo. (US); Shridhar Bharthulwar, Longmont, Colo. (US); and Paul E. Tinius, Broomfield, Colo. (US)
Assigned to EMC Corporation, Hopkinton, Mass. (US)
Filed on Oct. 03, 2006, as Appl. No. 11/538,316.
This patent is subject to a terminal disclaimer.
Int. Cl. G06F 12/00 (2006.01)

U.S. Cl. 707—204 [707/10; 707/200]

18 Claims

1. In a distributed computing system having a primary storage device, a secondary storage device and a policy engine server, the policy engine server being configured to manage migration of files between the primary and secondary storage devices by migrating data files on the primary storage device to the secondary storage device and replacing the data files on the primary storage device with a placeholder files, a method for locating placeholder files within the primary storage device that are not properly referenced by secondary files stored on the secondary storage device, the method comprising:

identifying a placeholder file stored on the primary storage device, the placeholder file including an offline reference to a secondary file stored on the secondary storage device, wherein the offline reference includes an address of the secondary file;

identifying the secondary file stored on secondary storage device and referenced by the address of the secondary file in the offline reference included in the placeholder file;

identifying an online reference included in the secondary file, wherein the online reference includes an address to a particular placeholder file on the primary storage device;

determining that the placeholder file is a missing parent file if the address to the particular placeholder file is not to the placeholder file; and

updating the online reference of the secondary file to include the file identification data of the placeholder file to properly identify the placeholder file.