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When the hashes are the same, and Netapp or ZFS compares and saves both, does it change the contents of one slightly to change the resulting hash, does it save some metadata note about which is which, put them in different parts of the file structure and link them to their correct sets...? How does it cope? Apologise for the stupid question, this is all beyond my ken really, but fascinating, I'd like to know how it gets resolved.