Hey folks!
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I'm a newbie to this forum, but not so in terms of technology, so here's my $0.02:
One thing to remember is that a true "backup" is supposed to save your butt if something "BAD" happens. So, the traditional concept of having backup on removable media is an important one because you want to store "some" of your backups
somewhere else (i.e. off-site).
This is because no matter how many backups one has, if they're all in the same location, fire, flood, earthquake, theft, etc, won't discriminate. For example, if you have a fire, all your data in the same room/house/office, etc can be destroyed. Similarly, if a thief decides to steal your server, they won't say, "Oh, the drives are RAID'd so I better leave one!"
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A typical backup regimen is one in which incremental backups are done in some period (say, daily), while full backups are done on a longer cycle (say, weekly) and selected full backups are stored off-site (say, monthly), on a rotational basis.
IMO, there's no such thing as a completely "foolproof" backup system ... depending on what you do, you'll either have more or less protection - that's all.
Cheers,
DH