| > What's your criteria for backup? Something like Attic, Borg, CrashPlan, Restic, etc, that allow snapshot retention periods, like "1 per year for the last X years, 1 per month for the last X months, one per day for the last X days". > I completely agree that something like RAID is not backup, but 30-60 days seems comparable to other backup services and covers most scenarios. That doesn't protect against bitrot. e.g. 1. File is backed up (snapshot A). 2. File is slightly corrupted by bitrot, cosmic ray, etc. 3. File is modified by user, corruption is unnoticed. 4. File is backed up again (snapshot B). 5. "Backup" service deletes snapshot A. 6. User discovers corruption. 7. User looks to restore earlier versions until an uncorrupted one is found. 8. User discovers that all available snapshots were made after corruption happened. Or replace "file" with "directory" and "bitrot" with "accidental file deletion" and the user still suffers from data loss. Mirrors are not backups, and a few revolving snapshot slots is effectively a mirror. |