4.3 - Backup methods and the 3-2-1 rule
CompTIA A+ Core 2 objective 4.3 covers backup methods and rotation schemes. A full backup on Sunday followed by copies of only the data changed since Sunday is a differential backup, while an incremental instead copies changes since the last backup of any kind. The 3-2-1 rule recommends keeping 3 copies of your data, on 2 different media, with 1 copy off-site. Grandfather-Father-Son (GFS) is a rotation that keeps daily, weekly and monthly sets on rotating media. Crucially, you must periodically test restoring from backups, not just create them, to confirm they are valid and recoverable. Expect scenario questions that describe a backup schedule or goal and ask which method, rule or rotation it matches, or why testing restores matters.
Full Sunday + only changes since Sunday = differential (incremental = changes since last backup of any type). 3-2-1 = 3 copies, 2 media, 1 off-site. Daily/weekly/monthly rotation = GFS. Always test restores.
Practice questions
1. A backup runs a full copy on Sunday and then only the data changed since Sunday each weekday. Which weekday backup type is this?
- An incremental backup
- A differential backup (correct answer)
- A full backup
- A snapshot backup
Differential backs up everything changed since the last FULL backup. Incremental backs up changes since the last backup of any type.
2. Following the 3-2-1 backup rule, what does it recommend?
- 3 passwords, 2 admins, and 1 server
- 3 copies, on 2 media, with 1 off-site (correct answer)
- 3 separate backups every hour
- One full backup and nothing else
3-2-1: keep 3 copies of data, on 2 different media, with 1 stored offsite (protects against local disasters).
3. A backup scheme keeps daily, weekly and monthly sets rotating media. This rotation is known as:
- A striped RAID array
- Grandfather-Father-Son (GFS) (correct answer)
- Scheduled disk defragmentation
- Real-time disk mirroring
GFS rotates daily(son), weekly(father) and monthly(grandfather) backups for retention and media reuse.
4. Why must you periodically TEST restoring from backups, not just create them?
- To deliberately use up disk space
- To confirm backups are valid and recoverable (correct answer)
- To intentionally slow down the network
- There is honestly no real reason
A backup is only useful if it restores — test restores to catch corruption, gaps or process errors before a real disaster.
5. What does the 3-2-1 backup rule specify?
- 3 passwords, 2 admins, 1 server
- 3 copies, on 2 media, with 1 off-site (correct answer)
- 3 separate backups every hour
- Keep the data for 321 days
3-2-1: keep 3 copies of data, on 2 different media types, with 1 copy off-site (or offline) — protecting against device, site and ransomware loss.
6. Before working inside a PC, what should a technician wear to prevent electrostatic damage?
- Insulated rubber work gloves
- An anti-static (ESD) wrist strap (correct answer)
- Impact-rated safety goggles
- A disposable dust filter mask
An ESD wrist strap grounds the technician, safely equalizing static charge before it damages components. Rubber gloves can worsen static; goggles/masks don't stop ESD.