US Patent 8055622 Immutable data containers in tiered storage hierarchies

System and method for providing immutable data containers in tiered storage hierarchies. Embodiments may allow fulfillment of regulatory requirements for retaining certain data through management of a user-defined policy. The policy may specify what data in the file system needs to be stored as immutable data to the immutable data container in the file system. File system data may be tracked, and data specified by the policy may be transparently and automatically stored to the immutable data container within the file system. Updates to the data specified by the policy may also be stored to the immutable data container. This may be performed without overwriting or modifying the earlier version(s) of the data stored to the immutable data container, and thus every version of the data specified by the policy may be stored to and, if necessary, reconstructed from the immutable data container.