A file system in a storage system allows a user to designate data as write-once read-many (WORM) data. The WORM data are stored in a first set of storage media of the storage system. Signature data are generated from the WORM data. Using the signature data, the integrity of the WORM data can be verified....http://www.google.com/patents/US20060126468?utm_source=gb-gplus-sharePatent US20060126468 - Method and apparatus for verifiably migrating WORM data
