Rule number whatever of backups: Don't discard old backups. Bitrot occurs, and people make mistakes, and newer backups can have flaws that older ones don't, which will go undiscovered until it's too late.

We're not talking about piles of tapes, we're talking about virtually unlimited disk space. State-of-the-art backup software chunks and deduplicates data and stores snapshots of directory trees. For most cases, there's no reason not to keep a subset of old snapshots, and many reasons to keep them.

I'd love to see BackBlaze offer the option to select "mission critical" folders that have super-long-life (Time Machine-like) version retention. Give everyone a few gigabytes of this for free, charge a premium to increase that space.

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.