I think the &#x27;three copies&#x27; rule refers to cyclic backups, not necessarily three copies of the one piece of data.<p>This protects against data corruption that is not detected immediately.<p>Another common way of doing this (and one that I prefer) is one where you rotate out a backup medium with ever larger intervals. So one gets set aside per week, then one gets set aside per month and so on. That gives you a series of snapshots in time that will allow you to pinpoint with some accuracy when an event happened. Longer ago you&#x27;ll have less accuracy but this can help a lot in trying to triangulate who or what messed up. Just being able to answer the question of whether or not &#x27;x&#x27; happened before &#x27;y&#x27; was hired or after can help in narrowing down the number of suspects in case of a breach or other nastiness. It also prevents against back-ups for whatever reason not wanting to be reloaded (and you should guard against that by loading your back-up immediately after you make it, even so, the medium might fail the next time you try a read).<p>Better still if there is a streaming log of everything but only very few companies can afford that sort of solution for all their data. Those can be hard to restore from (by replaying) so there too a snapshot system can help.