03
Section 03 · 5 guides
Backup & Sync
Three copies, two media, one off-site — and the four things people count twice. Copies, distance and versions, and how to tell a backup from a mirror.
- 3CopiesOf the data. Distinct copies — not one copy with three windows onto it.
- 2MediaDifferent kinds. Flash, spinning disk, tape, object storage — failures they do not share.
- 1Off-siteAnother building. Not another room, not the shelf beside the machine.
Everything in this section
Copies, media, distance, versions.
- How Many Copies Is EnoughThree copies, two media, one off-site — and where almost every setup stops short.
- Sync Is Not BackupA mirror propagates a deletion in seconds. One copy with several windows is still one copy.
- RAID Is Uptime, Not HistoryWhat redundancy buys, and the four things it does not survive.
- Versions, Retention and the Bad TuesdayHow far back you can actually go, and why that is the real question.
- An Untested Backup Is a HypothesisThe one afternoon a year that turns a hope into a fact.
The other rooms
Kept running by
The Bench Roll
Eleven names who keep the lights on in this room. Listed here, marked as what they are, and never mixed into the writing.
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