Patent ID: 7293027

Claim:
A method for protecting history in a file system in which rules governing which versions of files of the file system must be retained, and for how long, are enforced by one or more storage systems attached to a network, the method comprising: associating with a storage system a time standard configured to prevent the accuracy of the time standard from being manipulated over the network; storing versions of the files in the storage system, with each of the versions recording a state of one of the files, and with the versions of the files stored in a manner adapted to allow separate retrieval of versions of different ones of the files in any order; storing, in the storage system, directory information which is sufficient to allow a version of each of the files to be retrieved starting from a file system pathname; marking at least some of the versions of the files as archival file versions not subject to modification, and assigning an expiration time to each of the archival file versions; comparing the time standard with the expiration time assigned to an archival file version that is one of the archival file versions and, based at least in part on this comparison, preventing a storage system clients from deleting the archival file version before the expiration time assigned to it has passed; and allowing the storage system client to delete the archival file version after the expiration time assigned to it has passed; wherein no action taken by the storage system client can cause the expiration time assigned to the archival file version to be changed to an earlier time; wherein after the archival file version is deleted, storage space that was used to store it in the storage system is reused; and wherein, when deletion is allowed, the storage system client can delete the archival file version separately and independently from any others of the archival file versions regardless of the expiration times assigned to them.