I do it 3 ways.
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Critical stuff (photos, documents etc) is synced in realtime to backblaze. Low RPO. Low RTO.
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Critical stuff is also backed up to a secondary NAS 2x per day for versioned backups. And that data is synced nightly to Backblaze. Higher RPO but also Higher RTO.
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All data from secondary NAS/Backup NAS is backed up nightly to 1 of 3 large external hard drives that are rotated monthly. Each disk holds ~30 days of backup archives from #2.
- Most recently pulled disk is stored off site. Oldest disk is brought back on site but stored in a UL rated fire safe