State the 3-2-1 backup rule and its rationale.

• A. Keep at least three copies of data, on two different media, with one offsite copy to protect against site-wide disasters.
• B. Maintain two copies of data on a single medium and one copy in the cloud.
• C. Have three copies on one medium and two offsite backups.
• D. Use three backups all on the same disk to maximize speed.

Answer: (A)

You’re being tested on understanding the 3-2-1 backup rule: keep three total copies of your data, store them on at least two different storage media, and have one copy kept offsite. This setup gives you real protection: three copies means you’re unlikely to lose everything if one copy fails, using two different media reduces the chance that a single failure type wipes out all copies, and an offsite copy guards against local disasters such as fires, floods, or theft.

The best answer matches all parts exactly: three copies, across two different media, with one copy offsite. The other options fall short because they don’t ensure storage on multiple media or they don’t reliably separate at least one copy offsite, which weakens redundancy and disaster protection.