What actually counts as a copy under the 3-2-1 rule, why a RAID mirror or a snapshot only protects against one kind of failure, and the one-page inventory that exposes the gaps.
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Disclosure: this is my own article (Charles Hartmann, Homelab the Right Way). Written with AI help and edited by me; the setup described is mine.
But it feeeeels like a backup, and isn’t that what really matters? In my setup I have 3 drives (2x 8Tb, 1x 14 Tb) and I finally have the opportunity to do some consolidation and not just have 3 single drives plugged into a server. Zfs, raid , a dedicated backup drive, but I’m still figuring out what the layout should be.
Ha, it absolutely feels like one, right up until a bad sync or a fat-fingered rm hits every disk at once. With 2x8 TB plus a 14 TB, one layout people often land on is mirroring the two 8s (ZFS mirror) for live data and using the 14 TB as a separate backup target (snapshots replicated to it), plus something offsite for the stuff you can’t lose. That gets you redundancy and an actual backup out of the same three drives.
Put the two 8tb in a mirrored raid so if one fails you keep your data. Use the 14tb as a backup that is left unplugged for longevity.
That would be my recommendation which is similar to what I have (4 x 6 tb for twelve gigs of redundant storage) and a couple of 8tb drives I keep for occasional (monthly or so) archival backup.
I agree. This is also nice because if you need more space in the future you can always add 8TB drives in pairs.