Protecting data stored on CAS device presents an interesting dilemma for users because one of the primary purposes of a CAS product is to serve as a final resting place for data in an unchangeable format. HP deploys each of its SmartCell storage nodes in a mirrored configuration -- each node keeps a mirror of its partner's data. In the event that one-half of the mirror fails, a free node in the grid is allocated as a replacement partner to mirror the data; the failed mirror can then be repaired and reinserted in the grid.
EMC recommends replicating data to a second Centera at another site, but this is a costly alternative. To reduce the cost of a high-speed link between the two sites, the CBRM allows existing backup software to connect to the Centera and back up its data to tape using the NDMP protocol. CAS products from Bycast, IBM and allow you to copy each file or object to tape. However, this process reintroduces concerns about data integrity because someone needs to be responsible for moving the tape offsite and managing it in the long term.