This is from the StoreOnce / Catalyst Best Practices Guide:
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HP StoreOnce Catalyst has the additional advantage that backups can then be moved offsite to another catalyst store all under control of the software. The data is moved without rehydration i.e. only new data ‘chunks’ are moved between stores. It is possible to move to multiple stores. Data duplication uses the HP Data Protector ‘object copy’ functionality and can replicate data to multiple HP StoreOnce Catalyst stores.
This does not appear to be a HP INternal document, so I will attach a copy to this response